Techdebt: Replace string-format with f-strings (for tests dirs) (#5678)

tests/terraformtests/terraform-provider-aws

@@ -1 +1 @@
-Subproject commit f9a6db6e3c3f3299701747972fd6c37ba4af36f4
+Subproject commit 01a50d07400ee7513b31ec10e9832a2d8290b4e2

tests/test_acm/test_acm.py

@@ -511,7 +511,7 @@ def test_add_too_many_tags():
     with pytest.raises(ClientError) as ex:
         client.add_tags_to_certificate(
             CertificateArn=arn,
-            Tags=[{"Key": "a-%d" % i, "Value": "abcd"} for i in range(1, 52)],
+            Tags=[{"Key": f"a-{i}", "Value": "abcd"} for i in range(1, 52)],
         )
     ex.value.response["Error"]["Code"].should.equal("TooManyTagsException")
     ex.value.response["Error"]["Message"].should.contain("contains too many Tags")
@@ -520,7 +520,7 @@ def test_add_too_many_tags():
     # Add 49 tags first, then try to add 2 more.
     client.add_tags_to_certificate(
         CertificateArn=arn,
-        Tags=[{"Key": "p-%d" % i, "Value": "pqrs"} for i in range(1, 50)],
+        Tags=[{"Key": f"p-{i}", "Value": "pqrs"} for i in range(1, 50)],
     )
     client.list_tags_for_certificate(CertificateArn=arn)["Tags"].should.have.length_of(
         49

tests/test_apigateway/test_apigateway.py

@@ -931,12 +931,8 @@ def test_create_authorizer():
     response["ResponseMetadata"].pop("HTTPHeaders", None)
     response["ResponseMetadata"].pop("RetryAttempts", None)
 
-    response["items"][0]["id"].should.match(
+    response["items"][0]["id"].should.match(rf"{authorizer_id2}|{authorizer_id}")
-        r"{0}|{1}".format(authorizer_id2, authorizer_id)
+    response["items"][1]["id"].should.match(rf"{authorizer_id2}|{authorizer_id}")
-    )
-    response["items"][1]["id"].should.match(
-        r"{0}|{1}".format(authorizer_id2, authorizer_id)
-    )
 
     new_authorizer_name_with_vars = "authorizer_with_vars"
     response = client.create_authorizer(
@@ -1186,9 +1182,7 @@ def test_put_integration_validation():
         client.put_integration(
             restApiId=api_id,
             resourceId=root_id,
-            credentials="arn:aws:iam::{}:role/service-role/testfunction-role-oe783psq".format(
+            credentials=f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/testfunction-role-oe783psq",
-                ACCOUNT_ID
-            ),
             httpMethod="GET",
             type=_type,
             uri="arn:aws:apigateway:us-west-2:s3:path/b/k",
@@ -1210,9 +1204,7 @@ def test_put_integration_validation():
             client.put_integration(
                 restApiId=api_id,
                 resourceId=root_id,
-                credentials="arn:aws:iam::{}:role/service-role/testfunction-role-oe783psq".format(
+                credentials=f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/testfunction-role-oe783psq",
-                    ACCOUNT_ID
-                ),
                 httpMethod="GET",
                 type=_type,
                 uri="arn:aws:apigateway:us-west-2:s3:path/b/k",

tests/test_apigateway/test_apigateway_cloudformation.py

@@ -367,7 +367,7 @@ def test_simple_apigateway_with_lambda_proxy():
     statement = policy["Statement"][0]
     statement["FunctionName"].should.contain(fn_name)
     statement["Condition"]["ArnLike"]["AWS:SourceArn"].should.equal(
-        "arn:aws:execute-api:us-east-1:123456789012:{}/*/*".format(api_id)
+        f"arn:aws:execute-api:us-east-1:123456789012:{api_id}/*/*"
     )
 
 

tests/test_apigateway/test_apigateway_deployments.py

@@ -143,12 +143,8 @@ def test_create_multiple_deployments():
 
     response = client.get_deployments(restApiId=api_id)
 
-    response["items"][0]["id"].should.match(
+    response["items"][0]["id"].should.match(rf"{deployment_id2}|{deployment_id}")
-        r"{0}|{1}".format(deployment_id2, deployment_id)
+    response["items"][1]["id"].should.match(rf"{deployment_id2}|{deployment_id}")
-    )
-    response["items"][1]["id"].should.match(
-        r"{0}|{1}".format(deployment_id2, deployment_id)
-    )
 
 
 @mock_apigateway

tests/test_apigateway/test_server.py

@@ -34,16 +34,16 @@ def test_usage_plans_apis():
     json.loads(res.data)["item"].should.have.length_of(1)
 
     # Get single usage plan
-    res = test_client.get("/usageplans/{0}".format(created_plan["id"]))
+    res = test_client.get(f"/usageplans/{created_plan['id']}")
     fetched_plan = json.loads(res.data)
     fetched_plan.should.equal(created_plan)
 
     # Not existing usage plan
-    res = test_client.get("/usageplans/{0}".format("not_existing"))
+    res = test_client.get("/usageplans/not_existing")
     res.status_code.should.equal(404)
 
     # Delete usage plan
-    res = test_client.delete("/usageplans/{0}".format(created_plan["id"]))
+    res = test_client.delete(f"/usageplans/{created_plan['id']}")
     res.data.should.equal(b"{}")
 
     # List usage plans (expect empty again)
@@ -61,53 +61,45 @@ def test_usage_plans_keys():
     created_api_key = json.loads(res.data)
 
     # List usage plans keys (expect empty)
-    res = test_client.get("/usageplans/{0}/keys".format(usage_plan_id))
+    res = test_client.get(f"/usageplans/{usage_plan_id}/keys")
     json.loads(res.data)["item"].should.have.length_of(0)
 
     # Invalid api key (does not exists at all)
-    res = test_client.get(
+    res = test_client.get(f"/usageplans/{usage_plan_id}/keys/not_existing")
-        "/usageplans/{0}/keys/{1}".format(usage_plan_id, "not_existing")
-    )
     res.status_code.should.equal(404)
 
     # not existing usage plan with existing api key
-    res = test_client.get(
+    res = test_client.get(f"/usageplans/not_existing/keys/{created_api_key['id']}")
-        "/usageplans/{0}/keys/{1}".format("not_existing", created_api_key["id"])
-    )
     res.status_code.should.equal(404)
 
     # not jet added api key
-    res = test_client.get(
+    res = test_client.get(f"/usageplans/{usage_plan_id}/keys/{created_api_key['id']}")
-        "/usageplans/{0}/keys/{1}".format(usage_plan_id, created_api_key["id"])
-    )
     res.status_code.should.equal(404)
 
     # Create usage plan key
     res = test_client.post(
-        "/usageplans/{0}/keys".format(usage_plan_id),
+        f"/usageplans/{usage_plan_id}/keys",
         data=json.dumps({"keyId": created_api_key["id"], "keyType": "API_KEY"}),
     )
     created_usage_plan_key = json.loads(res.data)
 
     # List usage plans keys (expect 1 key)
-    res = test_client.get("/usageplans/{0}/keys".format(usage_plan_id))
+    res = test_client.get(f"/usageplans/{usage_plan_id}/keys")
     json.loads(res.data)["item"].should.have.length_of(1)
 
     # Get single usage plan key
-    res = test_client.get(
+    res = test_client.get(f"/usageplans/{usage_plan_id}/keys/{created_api_key['id']}")
-        "/usageplans/{0}/keys/{1}".format(usage_plan_id, created_api_key["id"])
-    )
     fetched_plan_key = json.loads(res.data)
     fetched_plan_key.should.equal(created_usage_plan_key)
 
     # Delete usage plan key
     res = test_client.delete(
-        "/usageplans/{0}/keys/{1}".format(usage_plan_id, created_api_key["id"])
+        f"/usageplans/{usage_plan_id}/keys/{created_api_key['id']}"
     )
     res.data.should.equal(b"{}")
 
     # List usage plans keys (expect to be empty again)
-    res = test_client.get("/usageplans/{0}/keys".format(usage_plan_id))
+    res = test_client.get(f"/usageplans/{usage_plan_id}/keys")
     json.loads(res.data)["item"].should.have.length_of(0)
 
 
@@ -118,7 +110,7 @@ def test_create_usage_plans_key_non_existent_api_key():
 
     # Create usage plan key with non-existent api key
     res = test_client.post(
-        "/usageplans/{0}/keys".format(usage_plan_id),
+        f"/usageplans/{usage_plan_id}/keys",
         data=json.dumps({"keyId": "non-existent", "keyType": "API_KEY"}),
     )
     res.status_code.should.equal(404)

tests/test_applicationautoscaling/test_applicationautoscaling.py

@@ -9,7 +9,7 @@ DEFAULT_ECS_CLUSTER = "default"
 DEFAULT_ECS_TASK = "test_ecs_task"
 DEFAULT_ECS_SERVICE = "sample-webapp"
 DEFAULT_SERVICE_NAMESPACE = "ecs"
-DEFAULT_RESOURCE_ID = "service/{}/{}".format(DEFAULT_ECS_CLUSTER, DEFAULT_ECS_SERVICE)
+DEFAULT_RESOURCE_ID = f"service/{DEFAULT_ECS_CLUSTER}/{DEFAULT_ECS_SERVICE}"
 DEFAULT_SCALABLE_DIMENSION = "ecs:service:DesiredCount"
 DEFAULT_MIN_CAPACITY = 1
 DEFAULT_MAX_CAPACITY = 1
@@ -122,12 +122,12 @@ def test_describe_scalable_targets_only_return_ecs_targets():
     register_scalable_target(
         client,
         ServiceNamespace="ecs",
-        ResourceId="service/{}/test1".format(DEFAULT_ECS_CLUSTER),
+        ResourceId=f"service/{DEFAULT_ECS_CLUSTER}/test1",
     )
     register_scalable_target(
         client,
         ServiceNamespace="ecs",
-        ResourceId="service/{}/test2".format(DEFAULT_ECS_CLUSTER),
+        ResourceId=f"service/{DEFAULT_ECS_CLUSTER}/test2",
     )
     register_scalable_target(
         client,
@@ -158,7 +158,7 @@ def test_describe_scalable_targets_next_token_success():
         register_scalable_target(
             client,
             ServiceNamespace="ecs",
-            ResourceId="service/{}/{}".format(DEFAULT_ECS_CLUSTER, i),
+            ResourceId=f"service/{DEFAULT_ECS_CLUSTER}/{i}",
         )
     response = client.describe_scalable_targets(
         ServiceNamespace=DEFAULT_SERVICE_NAMESPACE
@@ -379,9 +379,7 @@ def test_put_scaling_policy(policy_type, policy_body_kwargs):
     )
     response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
     response["PolicyARN"].should.match(
-        r"arn:aws:autoscaling:.*1:scalingPolicy:.*:resource/{}/{}:policyName/{}".format(
+        rf"arn:aws:autoscaling:.*1:scalingPolicy:.*:resource/{namespace}/{resource_id}:policyName/{policy_name}"
-            namespace, resource_id, policy_name
-        )
     )
 
 
@@ -434,9 +432,7 @@ def test_describe_scaling_policies():
     policy["PolicyType"].should.equal(policy_type)
     policy["TargetTrackingScalingPolicyConfiguration"].should.equal(policy_body)
     policy["PolicyARN"].should.match(
-        r"arn:aws:autoscaling:.*1:scalingPolicy:.*:resource/{}/{}:policyName/{}".format(
+        rf"arn:aws:autoscaling:.*1:scalingPolicy:.*:resource/{namespace}/{resource_id}:policyName/{policy_name}"
-            namespace, resource_id, policy_name
-        )
     )
     policy.should.have.key("CreationTime").which.should.be.a("datetime.datetime")
 

tests/test_applicationautoscaling/test_validation.py

@@ -12,7 +12,7 @@ DEFAULT_ECS_CLUSTER = "default"
 DEFAULT_ECS_TASK = "test_ecs_task"
 DEFAULT_ECS_SERVICE = "sample-webapp"
 DEFAULT_SERVICE_NAMESPACE = "ecs"
-DEFAULT_RESOURCE_ID = "service/{}/{}".format(DEFAULT_ECS_CLUSTER, DEFAULT_ECS_SERVICE)
+DEFAULT_RESOURCE_ID = f"service/{DEFAULT_ECS_CLUSTER}/{DEFAULT_ECS_SERVICE}"
 DEFAULT_SCALABLE_DIMENSION = "ecs:service:DesiredCount"
 DEFAULT_MIN_CAPACITY = 1
 DEFAULT_MAX_CAPACITY = 1
@@ -71,7 +71,7 @@ def test_describe_scalable_targets_with_multiple_invalid_parameters_should_retur
 @mock_applicationautoscaling
 def test_register_scalable_target_ecs_with_non_existent_service_should_return_clusternotfound_exception():
     client = boto3.client("application-autoscaling", region_name=DEFAULT_REGION)
-    resource_id = "service/{}/foo".format(DEFAULT_ECS_CLUSTER)
+    resource_id = f"service/{DEFAULT_ECS_CLUSTER}/foo"
 
     with pytest.raises(ClientError) as ex:
         register_scalable_target(client, ServiceNamespace="ecs", ResourceId=resource_id)

tests/test_autoscaling/test_autoscaling.py

@@ -99,7 +99,7 @@ def test_create_autoscaling_group_from_invalid_instance_id():
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.value.response["Error"]["Code"].should.equal("ValidationError")
     ex.value.response["Error"]["Message"].should.equal(
-        "Instance [{0}] is invalid.".format(invalid_instance_id)
+        f"Instance [{invalid_instance_id}] is invalid."
     )
 
 
@@ -518,9 +518,7 @@ def test_update_autoscaling_group_launch_config():
         AutoScalingGroupName="test_asg",
         LaunchConfigurationName="test_launch_configuration_new",
         MinSize=1,
-        VPCZoneIdentifier="{subnet1},{subnet2}".format(
+        VPCZoneIdentifier=f"{mocked_networking['subnet1']},{mocked_networking['subnet2']}",
-            subnet1=mocked_networking["subnet1"], subnet2=mocked_networking["subnet2"]
-        ),
         NewInstancesProtectedFromScaleIn=False,
     )
 
@@ -566,9 +564,7 @@ def test_update_autoscaling_group_launch_template():
             "Version": "1",
         },
         MinSize=1,
-        VPCZoneIdentifier="{subnet1},{subnet2}".format(
+        VPCZoneIdentifier=f"{mocked_networking['subnet1']},{mocked_networking['subnet2']}",
-            subnet1=mocked_networking["subnet1"], subnet2=mocked_networking["subnet2"]
-        ),
         NewInstancesProtectedFromScaleIn=False,
     )
 

tests/test_autoscaling/test_autoscaling_groups.py

@@ -61,7 +61,7 @@ class TestAutoScalingGroup(TestCase):
     def test_list_many_autoscaling_groups(self):
 
         for i in range(51):
-            self._create_group("TestGroup%d" % i)
+            self._create_group(f"TestGroup{i}")
 
         response = self.as_client.describe_auto_scaling_groups()
         groups = response["AutoScalingGroups"]

tests/test_autoscaling/test_elb.py

@@ -203,10 +203,7 @@ class TestAutoScalingELB(TestCase):
                 }
             ],
             TerminationPolicies=["OldestInstance", "NewestInstance"],
-            VPCZoneIdentifier="{subnet1},{subnet2}".format(
+            VPCZoneIdentifier=f"{self.mocked_networking['subnet1']},{self.mocked_networking['subnet2']}",
-                subnet1=self.mocked_networking["subnet1"],
-                subnet2=self.mocked_networking["subnet2"],
-            ),
         )
 
         self.as_client.put_scheduled_update_group_action(
@@ -231,10 +228,7 @@ class TestAutoScalingELB(TestCase):
         group["MinSize"].should.equal(INSTANCE_COUNT_GROUP)
         group["Instances"].should.have.length_of(INSTANCE_COUNT_GROUP)
         group["VPCZoneIdentifier"].should.equal(
-            "{subnet1},{subnet2}".format(
+            f"{self.mocked_networking['subnet1']},{self.mocked_networking['subnet2']}"
-                subnet1=self.mocked_networking["subnet1"],
-                subnet2=self.mocked_networking["subnet2"],
-            )
         )
         group["LaunchConfigurationName"].should.equal(self.lc_name)
         group["DefaultCooldown"].should.equal(60)

tests/test_autoscaling/test_launch_configurations.py

@@ -21,9 +21,7 @@ def test_create_launch_configuration():
         SecurityGroups=["default", "default2"],
         UserData="This is some user_data",
         InstanceMonitoring={"Enabled": True},
-        IamInstanceProfile="arn:aws:iam::{}:instance-profile/testing".format(
+        IamInstanceProfile=f"arn:aws:iam::{ACCOUNT_ID}:instance-profile/testing",
-            ACCOUNT_ID
-        ),
         SpotPrice="0.1",
     )
 
@@ -39,7 +37,7 @@ def test_create_launch_configuration():
     userdata.should.equal(b"This is some user_data")
     launch_config["InstanceMonitoring"].should.equal({"Enabled": True})
     launch_config["IamInstanceProfile"].should.equal(
-        "arn:aws:iam::{}:instance-profile/testing".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:instance-profile/testing"
     )
     launch_config["SpotPrice"].should.equal("0.1")
     launch_config["BlockDeviceMappings"].should.equal([])
@@ -56,9 +54,7 @@ def test_create_launch_configuration_with_block_device_mappings():
         SecurityGroups=["default", "default2"],
         UserData="This is some user_data",
         InstanceMonitoring={"Enabled": True},
-        IamInstanceProfile="arn:aws:iam::{}:instance-profile/testing".format(
+        IamInstanceProfile=f"arn:aws:iam::{ACCOUNT_ID}:instance-profile/testing",
-            ACCOUNT_ID
-        ),
         SpotPrice="0.1",
         BlockDeviceMappings=[
             {"DeviceName": "/dev/xvdb", "VirtualName": "ephemeral0"},
@@ -236,7 +232,7 @@ def test_launch_configuration_describe_paginated():
     conn = boto3.client("autoscaling", region_name="us-east-1")
     for i in range(51):
         conn.create_launch_configuration(
-            LaunchConfigurationName="TestLC%d" % i,
+            LaunchConfigurationName=f"TestLC{i}",
             ImageId=EXAMPLE_AMI_ID,
             InstanceType="t2.medium",
         )

tests/test_awslambda/test_lambda.py

@@ -60,17 +60,13 @@ def test_list_functions():
     v1 = [f for f in our_functions if f["Version"] == "1"][0]
     v1["Description"].should.equal("v2")
     v1["FunctionArn"].should.equal(
-        "arn:aws:lambda:{}:{}:function:{}:1".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}:1"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
 
     latest = [f for f in our_functions if f["Version"] == "$LATEST"][0]
     latest["Description"].should.equal("")
     latest["FunctionArn"].should.equal(
-        "arn:aws:lambda:{}:{}:function:{}:$LATEST".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}:$LATEST"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
 
 
@@ -125,9 +121,7 @@ def test_create_function_from_aws_bucket():
 
     result.should.have.key("FunctionName").equals(function_name)
     result.should.have.key("FunctionArn").equals(
-        "arn:aws:lambda:{}:{}:function:{}".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
     result.should.have.key("Runtime").equals("python2.7")
     result.should.have.key("Handler").equals("lambda_function.lambda_handler")
@@ -163,9 +157,7 @@ def test_create_function_from_zipfile():
     result.should.equal(
         {
             "FunctionName": function_name,
-            "FunctionArn": "arn:aws:lambda:{}:{}:function:{}".format(
+            "FunctionArn": f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}",
-                _lambda_region, ACCOUNT_ID, function_name
-            ),
             "Runtime": "python2.7",
             "Role": result["Role"],
             "Handler": "lambda_function.lambda_handler",
@@ -281,7 +273,7 @@ def test_get_function():
     result["Configuration"].pop("LastModified")
 
     result["Code"]["Location"].should.equal(
-        "s3://awslambda-{0}-tasks.s3-{0}.amazonaws.com/test.zip".format(_lambda_region)
+        f"s3://awslambda-{_lambda_region}-tasks.s3-{_lambda_region}.amazonaws.com/test.zip"
     )
     result["Code"]["RepositoryType"].should.equal("S3")
 
@@ -309,9 +301,7 @@ def test_get_function():
     result = conn.get_function(FunctionName=function_name, Qualifier="$LATEST")
     result["Configuration"]["Version"].should.equal("$LATEST")
     result["Configuration"]["FunctionArn"].should.equal(
-        "arn:aws:lambda:us-west-2:{}:function:{}:$LATEST".format(
+        f"arn:aws:lambda:us-west-2:{ACCOUNT_ID}:function:{function_name}:$LATEST"
-            ACCOUNT_ID, function_name
-        )
     )
 
     # Test get function when can't find function name
@@ -376,9 +366,7 @@ def test_get_function_configuration(key):
     )
     result["Version"].should.equal("$LATEST")
     result["FunctionArn"].should.equal(
-        "arn:aws:lambda:{}:{}:function:{}:$LATEST".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}:$LATEST"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
 
     # Test get function when can't find function name
@@ -591,7 +579,7 @@ def test_publish():
 
     # #SetComprehension ;-)
     published_arn = list({f["FunctionArn"] for f in our_functions} - {latest_arn})[0]
-    published_arn.should.contain("{}:1".format(function_name))
+    published_arn.should.contain(f"{function_name}:1")
 
     conn.delete_function(FunctionName=function_name, Qualifier="1")
 
@@ -639,9 +627,7 @@ def test_list_create_list_get_delete_list():
     )
     expected_function_result = {
         "Code": {
-            "Location": "s3://awslambda-{0}-tasks.s3-{0}.amazonaws.com/test.zip".format(
+            "Location": f"s3://awslambda-{_lambda_region}-tasks.s3-{_lambda_region}.amazonaws.com/test.zip",
-                _lambda_region
-            ),
             "RepositoryType": "S3",
         },
         "Configuration": {
@@ -673,9 +659,7 @@ def test_list_create_list_get_delete_list():
         f["FunctionArn"] for f in functions if f["FunctionName"] == function_name
     ][0]
     func_arn.should.equal(
-        "arn:aws:lambda:{}:{}:function:{}".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
     functions = conn.list_functions(FunctionVersion="ALL")["Functions"]
     our_functions = [f for f in functions if f["FunctionName"] == function_name]
@@ -683,9 +667,7 @@ def test_list_create_list_get_delete_list():
 
     latest = [f for f in our_functions if f["Version"] == "$LATEST"][0]
     latest["FunctionArn"].should.equal(
-        "arn:aws:lambda:{}:{}:function:{}:$LATEST".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}:$LATEST"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
     latest.pop("FunctionArn")
     latest.pop("LastModified")
@@ -694,17 +676,13 @@ def test_list_create_list_get_delete_list():
     published = [f for f in our_functions if f["Version"] != "$LATEST"][0]
     published["Version"].should.equal("1")
     published["FunctionArn"].should.equal(
-        "arn:aws:lambda:{}:{}:function:{}:1".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}:1"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
 
     func = conn.get_function(FunctionName=function_name)
 
     func["Configuration"]["FunctionArn"].should.equal(
-        "arn:aws:lambda:{}:{}:function:{}".format(
+        f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:function:{function_name}"
-            _lambda_region, ACCOUNT_ID, function_name
-        )
     )
 
     # this is hard to match against, so remove it
@@ -746,7 +724,7 @@ def test_get_function_created_with_zipfile():
     assert len(response["Code"]) == 2
     assert response["Code"]["RepositoryType"] == "S3"
     assert response["Code"]["Location"].startswith(
-        "s3://awslambda-{0}-tasks.s3-{0}.amazonaws.com".format(_lambda_region)
+        f"s3://awslambda-{_lambda_region}-tasks.s3-{_lambda_region}.amazonaws.com"
     )
     response.should.have.key("Configuration")
     config = response["Configuration"]
@@ -801,17 +779,18 @@ def test_list_versions_by_function():
     assert res["ResponseMetadata"]["HTTPStatusCode"] == 201
     versions = conn.list_versions_by_function(FunctionName=function_name)
     assert len(versions["Versions"]) == 3
-    assert versions["Versions"][0][
+    assert (
-        "FunctionArn"
+        versions["Versions"][0]["FunctionArn"]
-    ] == "arn:aws:lambda:us-west-2:{}:function:{}:$LATEST".format(
+        == f"arn:aws:lambda:us-west-2:{ACCOUNT_ID}:function:{function_name}:$LATEST"
-        ACCOUNT_ID, function_name
+    )
+    assert (
+        versions["Versions"][1]["FunctionArn"]
+        == f"arn:aws:lambda:us-west-2:{ACCOUNT_ID}:function:{function_name}:1"
+    )
+    assert (
+        versions["Versions"][2]["FunctionArn"]
+        == f"arn:aws:lambda:us-west-2:{ACCOUNT_ID}:function:{function_name}:2"
     )
-    assert versions["Versions"][1][
-        "FunctionArn"
-    ] == "arn:aws:lambda:us-west-2:{}:function:{}:1".format(ACCOUNT_ID, function_name)
-    assert versions["Versions"][2][
-        "FunctionArn"
-    ] == "arn:aws:lambda:us-west-2:{}:function:{}:2".format(ACCOUNT_ID, function_name)
 
     conn.create_function(
         FunctionName="testFunction_2",
@@ -826,10 +805,9 @@ def test_list_versions_by_function():
     )
     versions = conn.list_versions_by_function(FunctionName="testFunction_2")
     assert len(versions["Versions"]) == 1
-    assert versions["Versions"][0][
+    assert (
-        "FunctionArn"
+        versions["Versions"][0]["FunctionArn"]
-    ] == "arn:aws:lambda:us-west-2:{}:function:testFunction_2:$LATEST".format(
+        == f"arn:aws:lambda:us-west-2:{ACCOUNT_ID}:function:testFunction_2:$LATEST"
-        ACCOUNT_ID
     )
 
 
@@ -980,7 +958,7 @@ def test_update_function_zip(key):
     assert len(response["Code"]) == 2
     assert response["Code"]["RepositoryType"] == "S3"
     assert response["Code"]["Location"].startswith(
-        "s3://awslambda-{0}-tasks.s3-{0}.amazonaws.com".format(_lambda_region)
+        f"s3://awslambda-{_lambda_region}-tasks.s3-{_lambda_region}.amazonaws.com"
     )
 
     config = response["Configuration"]
@@ -1038,7 +1016,7 @@ def test_update_function_s3():
     assert len(response["Code"]) == 2
     assert response["Code"]["RepositoryType"] == "S3"
     assert response["Code"]["Location"].startswith(
-        "s3://awslambda-{0}-tasks.s3-{0}.amazonaws.com".format(_lambda_region)
+        f"s3://awslambda-{_lambda_region}-tasks.s3-{_lambda_region}.amazonaws.com"
     )
 
     config = response["Configuration"]

tests/test_awslambda/test_lambda_eventsourcemapping.py

@@ -238,7 +238,7 @@ def test_invoke_function_from_sqs_exception():
 
     entries = []
     for i in range(3):
-        body = {"uuid": str(uuid.uuid4()), "test": "test_{}".format(i)}
+        body = {"uuid": str(uuid.uuid4()), "test": f"test_{i}"}
         entry = {"Id": str(i), "MessageBody": json.dumps(body)}
         entries.append(entry)
 

tests/test_awslambda/test_lambda_layers.py

@@ -65,9 +65,7 @@ def test_get_lambda_layers():
     for version in result["LayerVersions"]:
         version.pop("CreatedDate")
     result["LayerVersions"].sort(key=lambda x: x["Version"])
-    expected_arn = "arn:aws:lambda:{0}:{1}:layer:{2}:".format(
+    expected_arn = f"arn:aws:lambda:{_lambda_region}:{ACCOUNT_ID}:layer:{layer_name}:"
-        _lambda_region, ACCOUNT_ID, layer_name
-    )
     result["LayerVersions"].should.equal(
         [
             {

tests/test_awslambda/test_lambda_tags.py

@@ -106,15 +106,15 @@ def test_tags_not_found():
     """
     conn = boto3.client("lambda", _lambda_region)
     conn.list_tags.when.called_with(
-        Resource="arn:aws:lambda:{}:function:not-found".format(ACCOUNT_ID)
+        Resource=f"arn:aws:lambda:{ACCOUNT_ID}:function:not-found"
     ).should.throw(botocore.client.ClientError)
 
     conn.tag_resource.when.called_with(
-        Resource="arn:aws:lambda:{}:function:not-found".format(ACCOUNT_ID),
+        Resource=f"arn:aws:lambda:{ACCOUNT_ID}:function:not-found",
         Tags=dict(spam="eggs"),
     ).should.throw(botocore.client.ClientError)
 
     conn.untag_resource.when.called_with(
-        Resource="arn:aws:lambda:{}:function:not-found".format(ACCOUNT_ID),
+        Resource=f"arn:aws:lambda:{ACCOUNT_ID}:function:not-found",
         TagKeys=["spam"],
     ).should.throw(botocore.client.ClientError)

tests/test_awslambda/utilities.py

@@ -30,7 +30,12 @@ def lambda_handler(event, context):
 
 
 def get_test_zip_file2():
-    func_str = """
+    base_url = (
+        "motoserver:5000"
+        if settings.TEST_SERVER_MODE
+        else "ec2.us-west-2.amazonaws.com"
+    )
+    func_str = f"""
 import boto3
 
 def lambda_handler(event, context):
@@ -40,11 +45,7 @@ def lambda_handler(event, context):
     vol = ec2.Volume(volume_id)
 
     return {{'id': vol.id, 'state': vol.state, 'size': vol.size}}
-""".format(
+"""
-        base_url="motoserver:5000"
-        if settings.TEST_SERVER_MODE
-        else "ec2.us-west-2.amazonaws.com"
-    )
     return _process_lambda(func_str)
 
 

tests/test_batch/test_batch_jobs.py

@@ -385,9 +385,7 @@ def _wait_for_job_statuses(client, job_id, statuses, seconds_to_wait=30):
         time.sleep(0.1)
     else:
         raise RuntimeError(
-            "Time out waiting for job status {status}!\n Last status: {last_status}".format(
+            f"Time out waiting for job status {statuses}!\n Last status: {last_job_status}"
-                status=statuses, last_status=last_job_status
-            )
         )
 
 

tests/test_batch/test_batch_task_definition.py

@@ -18,7 +18,7 @@ def test_register_task_definition(use_resource_reqs):
     resp.should.contain("revision")
 
     assert resp["jobDefinitionArn"].endswith(
-        "{0}:{1}".format(resp["jobDefinitionName"], resp["revision"])
+        f"{resp['jobDefinitionName']}:{resp['revision']}"
     )
 
 
@@ -113,7 +113,7 @@ def test_reregister_task_definition(use_resource_reqs):
     resp1.should.contain("revision")
 
     assert resp1["jobDefinitionArn"].endswith(
-        "{0}:{1}".format(resp1["jobDefinitionName"], resp1["revision"])
+        f"{resp1['jobDefinitionName']}:{resp1['revision']}"
     )
     resp1["revision"].should.equal(1)
 

tests/test_cloudformation/test_cloudformation_custom_resources.py

@@ -12,7 +12,7 @@ from .fixtures.custom_lambda import get_template
 
 
 def get_lambda_code():
-    pfunc = """
+    return f"""
 def lambda_handler(event, context):
     # Need to print this, one of the tests verifies the correct input
     print(event)
@@ -21,17 +21,14 @@ def lambda_handler(event, context):
     response["StackId"] = event["StackId"]
     response["RequestId"] = event["RequestId"]
     response["LogicalResourceId"] = event["LogicalResourceId"]
-    response["PhysicalResourceId"] = "{resource_id}"
+    response["PhysicalResourceId"] = "CustomResource{str(uuid4())[0:6]}"
     response_data = dict()
     response_data["info_value"] = "special value"
     if event["RequestType"] == "Create":
         response["Data"] = response_data
     import cfnresponse
     cfnresponse.send(event, context, cfnresponse.SUCCESS, response_data)
-""".format(
+"""
-        resource_id=f"CustomResource{str(uuid4())[0:6]}"
-    )
-    return pfunc
 
 
 @mock_cloudformation

tests/test_cloudformation/test_cloudformation_depends_on.py

@@ -112,9 +112,7 @@ def test_create_stack_with_depends_on():
 
     ecs = boto3.client("ecs", region_name="us-east-1")
     cluster_arn = ecs.list_clusters()["clusterArns"][0]
-    assert cluster_arn == "arn:aws:ecs:us-east-1:{}:cluster/test-cluster".format(
+    assert cluster_arn == f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test-cluster"
-        ACCOUNT_ID
-    )
 
 
 @mock_cloudformation

tests/test_cloudformation/test_cloudformation_stack_crud_boto3.py

@@ -1075,10 +1075,10 @@ def test_creating_stacks_across_regions():
     list(west2_cf.stacks.all()).should.have.length_of(1)
 
     list(west1_cf.stacks.all())[0].stack_id.should.contain(
-        "arn:aws:cloudformation:us-west-1:{}:stack/test_stack/".format(ACCOUNT_ID)
+        f"arn:aws:cloudformation:us-west-1:{ACCOUNT_ID}:stack/test_stack/"
     )
     list(west2_cf.stacks.all())[0].stack_id.should.contain(
-        "arn:aws:cloudformation:us-west-2:{}:stack/test_stack/".format(ACCOUNT_ID)
+        f"arn:aws:cloudformation:us-west-2:{ACCOUNT_ID}:stack/test_stack/"
     )
 
 
@@ -1110,7 +1110,7 @@ def test_create_stack_with_notification_arn():
     messages.should.have.length_of(1)
     msg = json.loads(messages[0].body)
     msg["Subject"].should.equal("AWS CloudFormation Notification")
-    msg["Message"].should.contain("StackId='{}'\n".format(stack.stack_id))
+    msg["Message"].should.contain(f"StackId='{stack.stack_id}'\n")
     msg["Message"].should.contain("LogicalResourceId='test_stack_with_notifications'\n")
     msg["Message"].should.contain("ResourceStatus='CREATE_IN_PROGRESS'\n")
     msg["Message"].should.contain("ResourceStatusReason='User Initiated'\n")
@@ -1128,7 +1128,7 @@ def test_create_stack_with_notification_arn():
     messages = queue.receive_messages()
     messages.should.have.length_of(1)
     msg = json.loads(messages[0].body)
-    msg["Message"].should.contain("StackId='{}'\n".format(stack.stack_id))
+    msg["Message"].should.contain(f"StackId='{stack.stack_id}'\n")
     msg["Message"].should.contain("LogicalResourceId='test_stack_with_notifications'\n")
     msg["Message"].should.contain("ResourceStatus='CREATE_COMPLETE'\n")
     msg["Message"].should.contain("ResourceStatusReason='None'\n")
@@ -1150,10 +1150,10 @@ def test_create_stack_with_role_arn():
     cf.create_stack(
         StackName="test_stack_with_notifications",
         TemplateBody=dummy_template_json,
-        RoleARN="arn:aws:iam::{}:role/moto".format(ACCOUNT_ID),
+        RoleARN=f"arn:aws:iam::{ACCOUNT_ID}:role/moto",
     )
     stack = list(cf.stacks.all())[0]
-    stack.role_arn.should.equal("arn:aws:iam::{}:role/moto".format(ACCOUNT_ID))
+    stack.role_arn.should.equal(f"arn:aws:iam::{ACCOUNT_ID}:role/moto")
 
 
 @mock_cloudformation
@@ -1380,11 +1380,11 @@ def test_create_change_set_from_s3_url():
         Tags=[{"Key": "tag-key", "Value": "tag-value"}],
     )
     assert (
-        "arn:aws:cloudformation:us-west-1:{}:changeSet/NewChangeSet/".format(ACCOUNT_ID)
+        f"arn:aws:cloudformation:us-west-1:{ACCOUNT_ID}:changeSet/NewChangeSet/"
         in response["Id"]
     )
     assert (
-        "arn:aws:cloudformation:us-west-1:{}:stack/NewStack".format(ACCOUNT_ID)
+        f"arn:aws:cloudformation:us-west-1:{ACCOUNT_ID}:stack/NewStack"
         in response["StackId"]
     )
 
@@ -1503,9 +1503,7 @@ def test_execute_change_set_w_name():
 def test_describe_stack_pagination():
     conn = boto3.client("cloudformation", region_name="us-east-1")
     for i in range(100):
-        conn.create_stack(
+        conn.create_stack(StackName=f"test_stack_{i}", TemplateBody=dummy_template_json)
-            StackName="test_stack_{}".format(i), TemplateBody=dummy_template_json
-        )
 
     resp = conn.describe_stacks()
     stacks = resp["Stacks"]
@@ -1789,7 +1787,7 @@ def test_describe_updated_stack():
 
     cf_conn.update_stack(
         StackName="test_stack",
-        RoleARN="arn:aws:iam::{}:role/moto".format(ACCOUNT_ID),
+        RoleARN=f"arn:aws:iam::{ACCOUNT_ID}:role/moto",
         TemplateBody=dummy_update_template_json,
         Tags=[{"Key": "foo", "Value": "baz"}],
         Parameters=[{"ParameterKey": "KeyName", "ParameterValue": "value"}],
@@ -1801,7 +1799,7 @@ def test_describe_updated_stack():
     stack_by_id["StackId"].should.equal(stack["StackId"])
     stack_by_id["StackName"].should.equal("test_stack")
     stack_by_id["StackStatus"].should.equal("UPDATE_COMPLETE")
-    stack_by_id["RoleARN"].should.equal("arn:aws:iam::{}:role/moto".format(ACCOUNT_ID))
+    stack_by_id["RoleARN"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:role/moto")
     stack_by_id["Tags"].should.equal([{"Key": "foo", "Value": "baz"}])
 
     # Verify the updated template is persisted
@@ -1937,9 +1935,7 @@ def test_update_stack_when_rolled_back():
     err = ex.value.response["Error"]
     err.should.have.key("Code").being.equal("ValidationError")
     err.should.have.key("Message").match(
-        r"Stack:arn:aws:cloudformation:us-east-1:{}:stack/test_stack/[a-z0-9-]+ is in ROLLBACK_COMPLETE state and can not be updated.".format(
+        rf"Stack:arn:aws:cloudformation:us-east-1:{ACCOUNT_ID}:stack/test_stack/[a-z0-9-]+ is in ROLLBACK_COMPLETE state and can not be updated."
-            ACCOUNT_ID
-        )
     )
 
 
@@ -2121,7 +2117,7 @@ def test_list_exports_with_token():
         # Add index to ensure name is unique
         dummy_output_template["Outputs"]["StackVPC"]["Export"]["Name"] += str(i)
         cf.create_stack(
-            StackName="test_stack_{}".format(i),
+            StackName=f"test_stack_{i}",
             TemplateBody=json.dumps(dummy_output_template),
         )
     exports = cf.list_exports()

tests/test_cloudformation/test_cloudformation_stack_integration.py

@@ -52,7 +52,7 @@ def test_fn_join_boto3():
 
     stack = cf.describe_stacks()["Stacks"][0]
     fn_join_output = stack["Outputs"][0]
-    fn_join_output["OutputValue"].should.equal("test eip:{0}".format(eip["PublicIp"]))
+    fn_join_output["OutputValue"].should.equal(f"test eip:{eip['PublicIp']}")
 
 
 @mock_cloudformation
@@ -301,9 +301,7 @@ def lambda_handler(event, context):
         [
             {
                 "Version": 1,
-                "LayerVersionArn": "arn:aws:lambda:{}:{}:layer:{}:1".format(
+                "LayerVersionArn": f"arn:aws:lambda:{region}:{ACCOUNT_ID}:layer:{layer_name}:1",
-                    region, ACCOUNT_ID, layer_name
-                ),
                 "CompatibleRuntimes": ["python2.7", "python3.6"],
                 "Description": "Test Layer",
                 "LicenseInfo": "MIT",
@@ -424,7 +422,7 @@ def test_stack_spot_fleet():
                 "Type": "AWS::EC2::SpotFleet",
                 "Properties": {
                     "SpotFleetRequestConfigData": {
-                        "IamFleetRole": "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID),
+                        "IamFleetRole": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet",
                         "SpotPrice": "0.12",
                         "TargetCapacity": 6,
                         "AllocationStrategy": "diversified",
@@ -445,9 +443,7 @@ def test_stack_spot_fleet():
                                 "SecurityGroups": [{"GroupId": "sg-123"}],
                                 "SubnetId": subnet_id,
                                 "IamInstanceProfile": {
-                                    "Arn": "arn:aws:iam::{}:role/fleet".format(
+                                    "Arn": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"
-                                        ACCOUNT_ID
-                                    )
                                 },
                                 "WeightedCapacity": "4",
                                 "SpotPrice": "10.00",
@@ -480,7 +476,7 @@ def test_stack_spot_fleet():
     spot_fleet_config["SpotPrice"].should.equal("0.12")
     spot_fleet_config["TargetCapacity"].should.equal(6)
     spot_fleet_config["IamFleetRole"].should.equal(
-        "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"
     )
     spot_fleet_config["AllocationStrategy"].should.equal("diversified")
     spot_fleet_config["FulfilledCapacity"].should.equal(6.0)
@@ -513,7 +509,7 @@ def test_stack_spot_fleet_should_figure_out_default_price():
                 "Type": "AWS::EC2::SpotFleet",
                 "Properties": {
                     "SpotFleetRequestConfigData": {
-                        "IamFleetRole": "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID),
+                        "IamFleetRole": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet",
                         "TargetCapacity": 6,
                         "AllocationStrategy": "diversified",
                         "LaunchSpecifications": [
@@ -532,9 +528,7 @@ def test_stack_spot_fleet_should_figure_out_default_price():
                                 "SecurityGroups": [{"GroupId": "sg-123"}],
                                 "SubnetId": subnet_id,
                                 "IamInstanceProfile": {
-                                    "Arn": "arn:aws:iam::{}:role/fleet".format(
+                                    "Arn": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"
-                                        ACCOUNT_ID
-                                    )
                                 },
                                 "WeightedCapacity": "4",
                             },

tests/test_cloudwatch/test_cloudwatch_alarms.py

@@ -19,8 +19,8 @@ def test_create_alarm():
         Dimensions=[{"Name": "InstanceId", "Value": "i-0123457"}],
         EvaluationPeriods=5,
         InsufficientDataActions=["arn:insufficient"],
-        Namespace="{0}_namespace".format(name),
+        Namespace=f"{name}_namespace",
-        MetricName="{0}_metric".format(name),
+        MetricName=f"{name}_metric",
         OKActions=["arn:ok"],
         Period=60,
         Statistic="Average",
@@ -48,7 +48,7 @@ def test_create_alarm():
     alarm.should.have.key("InsufficientDataActions").equal(["arn:insufficient"])
     alarm.should.have.key("Unit").equal("Seconds")
     alarm.should.have.key("AlarmArn").equal(
-        "arn:aws:cloudwatch:{}:{}:alarm:{}".format(region, ACCOUNT_ID, name)
+        f"arn:aws:cloudwatch:{region}:{ACCOUNT_ID}:alarm:{name}"
     )
     # default value should be True
     alarm.should.have.key("ActionsEnabled").equal(True)
@@ -70,8 +70,8 @@ def test_delete_alarm():
         Dimensions=[{"Name": "InstanceId", "Value": "i-0123457"}],
         EvaluationPeriods=5,
         InsufficientDataActions=["arn:insufficient"],
-        Namespace="{0}_namespace".format(name),
+        Namespace=f"{name}_namespace",
-        MetricName="{0}_metric".format(name),
+        MetricName=f"{name}_metric",
         OKActions=["arn:ok"],
         Period=60,
         Statistic="Average",

tests/test_codebuild/test_codebuild.py

@@ -27,9 +27,7 @@ def test_codebuild_create_project_s3_artifacts():
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
 
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     response = client.create_project(
@@ -78,9 +76,7 @@ def test_codebuild_create_project_no_artifacts():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     response = client.create_project(
@@ -127,9 +123,7 @@ def test_codebuild_create_project_with_invalid_name():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     with pytest.raises(client.exceptions.from_code("InvalidInputException")) as err:
@@ -160,9 +154,7 @@ def test_codebuild_create_project_with_invalid_name_length():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     with pytest.raises(client.exceptions.from_code("InvalidInputException")) as err:
@@ -192,9 +184,7 @@ def test_codebuild_create_project_when_exists():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -234,9 +224,7 @@ def test_codebuild_list_projects():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -275,9 +263,7 @@ def test_codebuild_list_builds_for_project_no_history():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -309,9 +295,7 @@ def test_codebuild_list_builds_for_project_with_history():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -392,9 +376,7 @@ def test_codebuild_start_build_no_overrides():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -426,9 +408,7 @@ def test_codebuild_start_build_multiple_times():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -463,9 +443,7 @@ def test_codebuild_start_build_with_overrides():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     branch_override = "fix/testing"
@@ -504,9 +482,7 @@ def test_codebuild_batch_get_builds_1_project():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -543,9 +519,7 @@ def test_codebuild_batch_get_builds_2_projects():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -584,7 +558,7 @@ def test_codebuild_batch_get_builds_invalid_build_id():
     client = boto3.client("codebuild", region_name="eu-central-1")
 
     with pytest.raises(client.exceptions.InvalidInputException) as err:
-        client.batch_get_builds(ids=["some_project{}".format(uuid1())])
+        client.batch_get_builds(ids=[f"some_project{uuid1()}"])
     err.value.response["Error"]["Code"].should.equal("InvalidInputException")
 
 
@@ -613,9 +587,7 @@ def test_codebuild_delete_project():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -653,9 +625,7 @@ def test_codebuild_stop_build():
     environment["image"] = "contents_not_validated"
     environment["computeType"] = "BUILD_GENERAL1_SMALL"
     service_role = (
-        "arn:aws:iam::{0}:role/service-role/my-codebuild-service-role".format(
+        f"arn:aws:iam::{ACCOUNT_ID}:role/service-role/my-codebuild-service-role"
-            ACCOUNT_ID
-        )
     )
 
     client.create_project(
@@ -678,7 +648,7 @@ def test_codebuild_stop_build_no_build():
     client = boto3.client("codebuild", region_name="eu-central-1")
 
     with pytest.raises(client.exceptions.ResourceNotFoundException) as err:
-        client.stop_build(id="some_project:{0}".format(uuid1()))
+        client.stop_build(id=f"some_project:{uuid1()}")
     err.value.response["Error"]["Code"].should.equal("ResourceNotFoundException")
 
 
@@ -687,5 +657,5 @@ def test_codebuild_stop_build_bad_uid():
     client = boto3.client("codebuild", region_name="eu-central-1")
 
     with pytest.raises(client.exceptions.InvalidInputException) as err:
-        client.stop_build(id="some_project{0}".format(uuid1()))
+        client.stop_build(id=f"some_project{uuid1()}")
     err.value.response["Error"]["Code"].should.equal("InvalidInputException")

tests/test_codecommit/test_codecommit.py

@@ -24,19 +24,13 @@ def test_create_repository():
         "description repo one"
     )
     response["repositoryMetadata"]["cloneUrlSsh"].should.equal(
-        "ssh://git-codecommit.{0}.amazonaws.com/v1/repos/{1}".format(
+        "ssh://git-codecommit.eu-central-1.amazonaws.com/v1/repos/repository_one"
-            "eu-central-1", "repository_one"
-        )
     )
     response["repositoryMetadata"]["cloneUrlHttp"].should.equal(
-        "https://git-codecommit.{0}.amazonaws.com/v1/repos/{1}".format(
+        "https://git-codecommit.eu-central-1.amazonaws.com/v1/repos/repository_one"
-            "eu-central-1", "repository_one"
-        )
     )
     response["repositoryMetadata"]["Arn"].should.equal(
-        "arn:aws:codecommit:{0}:{1}:{2}".format(
+        f"arn:aws:codecommit:eu-central-1:{ACCOUNT_ID}:repository_one"
-            "eu-central-1", ACCOUNT_ID, "repository_one"
-        )
     )
     response["repositoryMetadata"]["accountId"].should.equal(ACCOUNT_ID)
 
@@ -58,19 +52,13 @@ def test_create_repository_without_description():
     response["repositoryMetadata"]["lastModifiedDate"].should_not.be.none
     response["repositoryMetadata"]["repositoryId"].should_not.be.empty
     response["repositoryMetadata"]["cloneUrlSsh"].should.equal(
-        "ssh://git-codecommit.{0}.amazonaws.com/v1/repos/{1}".format(
+        "ssh://git-codecommit.eu-central-1.amazonaws.com/v1/repos/repository_two"
-            "eu-central-1", "repository_two"
-        )
     )
     response["repositoryMetadata"]["cloneUrlHttp"].should.equal(
-        "https://git-codecommit.{0}.amazonaws.com/v1/repos/{1}".format(
+        "https://git-codecommit.eu-central-1.amazonaws.com/v1/repos/repository_two"
-            "eu-central-1", "repository_two"
-        )
     )
     response["repositoryMetadata"]["Arn"].should.equal(
-        "arn:aws:codecommit:{0}:{1}:{2}".format(
+        f"arn:aws:codecommit:eu-central-1:{ACCOUNT_ID}:repository_two"
-            "eu-central-1", ACCOUNT_ID, "repository_two"
-        )
     )
     response["repositoryMetadata"]["accountId"].should.equal(ACCOUNT_ID)
 
@@ -91,7 +79,7 @@ def test_create_repository_repository_name_exists():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("RepositoryNameExistsException")
     ex.response["Error"]["Message"].should.equal(
-        "Repository named {0} already exists".format("repository_two")
+        "Repository named repository_two already exists"
     )
 
 
@@ -138,19 +126,13 @@ def test_get_repository():
         "description repo one"
     )
     response.get("repositoryMetadata").get("cloneUrlSsh").should.equal(
-        "ssh://git-codecommit.{0}.amazonaws.com/v1/repos/{1}".format(
+        "ssh://git-codecommit.eu-central-1.amazonaws.com/v1/repos/repository_one"
-            "eu-central-1", "repository_one"
-        )
     )
     response.get("repositoryMetadata").get("cloneUrlHttp").should.equal(
-        "https://git-codecommit.{0}.amazonaws.com/v1/repos/{1}".format(
+        "https://git-codecommit.eu-central-1.amazonaws.com/v1/repos/repository_one"
-            "eu-central-1", "repository_one"
-        )
     )
     response.get("repositoryMetadata").get("Arn").should.equal(
-        "arn:aws:codecommit:{0}:{1}:{2}".format(
+        f"arn:aws:codecommit:eu-central-1:{ACCOUNT_ID}:repository_one"
-            "eu-central-1", ACCOUNT_ID, "repository_one"
-        )
     )
     response.get("repositoryMetadata").get("accountId").should.equal(ACCOUNT_ID)
 
@@ -162,9 +144,7 @@ def test_get_repository():
     ex.operation_name.should.equal("GetRepository")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("RepositoryDoesNotExistException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"{repository_name} does not exist")
-        "{0} does not exist".format(repository_name)
-    )
 
 
 @mock_codecommit

tests/test_codepipeline/test_codepipeline.py

@@ -459,7 +459,7 @@ def test_list_tags_for_resource():
     create_basic_codepipeline(client, name)
 
     response = client.list_tags_for_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name)
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}"
     )
     response["tags"].should.equal([{"key": "key", "value": "value"}])
 
@@ -488,12 +488,12 @@ def test_tag_resource():
     create_basic_codepipeline(client, name)
 
     client.tag_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name),
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}",
         tags=[{"key": "key-2", "value": "value-2"}],
     )
 
     response = client.list_tags_for_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name)
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}"
     )
     response["tags"].should.equal(
         [{"key": "key", "value": "value"}, {"key": "key-2", "value": "value-2"}]
@@ -521,7 +521,7 @@ def test_tag_resource_errors():
 
     with pytest.raises(ClientError) as e:
         client.tag_resource(
-            resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name),
+            resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}",
             tags=[{"key": "aws:key", "value": "value"}],
         )
     ex = e.value
@@ -536,20 +536,15 @@ def test_tag_resource_errors():
 
     with pytest.raises(ClientError) as e:
         client.tag_resource(
-            resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name),
+            resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}",
-            tags=[
+            tags=[{"key": f"key-{i}", "value": f"value-{i}"} for i in range(50)],
-                {"key": "key-{}".format(i), "value": "value-{}".format(i)}
-                for i in range(50)
-            ],
         )
     ex = e.value
     ex.operation_name.should.equal("TagResource")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("TooManyTagsException")
     ex.response["Error"]["Message"].should.equal(
-        "Tag limit exceeded for resource [arn:aws:codepipeline:us-east-1:123456789012:{}].".format(
+        f"Tag limit exceeded for resource [arn:aws:codepipeline:us-east-1:123456789012:{name}]."
-            name
-        )
     )
 
 
@@ -560,23 +555,23 @@ def test_untag_resource():
     create_basic_codepipeline(client, name)
 
     response = client.list_tags_for_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name)
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}"
     )
     response["tags"].should.equal([{"key": "key", "value": "value"}])
 
     client.untag_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name),
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}",
         tagKeys=["key"],
     )
 
     response = client.list_tags_for_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name)
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}"
     )
     response["tags"].should.have.length_of(0)
 
     # removing a not existing tag should raise no exception
     client.untag_resource(
-        resourceArn="arn:aws:codepipeline:us-east-1:123456789012:{}".format(name),
+        resourceArn=f"arn:aws:codepipeline:us-east-1:123456789012:{name}",
         tagKeys=["key"],
     )
 

tests/test_cognitoidentity/test_cognitoidentity.py

@@ -44,9 +44,7 @@ def test_create_identity_pool():
         AllowUnauthenticatedIdentities=False,
         SupportedLoginProviders={"graph.facebook.com": "123456789012345"},
         DeveloperProviderName="devname",
-        OpenIdConnectProviderARNs=[
+        OpenIdConnectProviderARNs=[f"arn:aws:rds:eu-west-2:{ACCOUNT_ID}:db:mysql-db"],
-            "arn:aws:rds:eu-west-2:{}:db:mysql-db".format(ACCOUNT_ID)
-        ],
         CognitoIdentityProviders=[
             {
                 "ProviderName": "testprovider",
@@ -54,7 +52,7 @@ def test_create_identity_pool():
                 "ServerSideTokenCheck": True,
             }
         ],
-        SamlProviderARNs=["arn:aws:rds:eu-west-2:{}:db:mysql-db".format(ACCOUNT_ID)],
+        SamlProviderARNs=[f"arn:aws:rds:eu-west-2:{ACCOUNT_ID}:db:mysql-db"],
     )
     assert result["IdentityPoolId"] != ""
 
@@ -68,9 +66,7 @@ def test_describe_identity_pool():
         AllowUnauthenticatedIdentities=False,
         SupportedLoginProviders={"graph.facebook.com": "123456789012345"},
         DeveloperProviderName="devname",
-        OpenIdConnectProviderARNs=[
+        OpenIdConnectProviderARNs=[f"arn:aws:rds:eu-west-2:{ACCOUNT_ID}:db:mysql-db"],
-            "arn:aws:rds:eu-west-2:{}:db:mysql-db".format(ACCOUNT_ID)
-        ],
         CognitoIdentityProviders=[
             {
                 "ProviderName": "testprovider",
@@ -78,7 +74,7 @@ def test_describe_identity_pool():
                 "ServerSideTokenCheck": True,
             }
         ],
-        SamlProviderARNs=["arn:aws:rds:eu-west-2:{}:db:mysql-db".format(ACCOUNT_ID)],
+        SamlProviderARNs=[f"arn:aws:rds:eu-west-2:{ACCOUNT_ID}:db:mysql-db"],
     )
 
     result = conn.describe_identity_pool(IdentityPoolId=res["IdentityPoolId"])

tests/test_cognitoidp/test_cognitoidp.py

@@ -35,9 +35,7 @@ def test_create_user_pool():
 
     result["UserPool"]["Id"].should.match(r"[\w-]+_[0-9a-zA-Z]+")
     result["UserPool"]["Arn"].should.equal(
-        "arn:aws:cognito-idp:us-west-2:{}:userpool/{}".format(
+        f"arn:aws:cognito-idp:us-west-2:{ACCOUNT_ID}:userpool/{result['UserPool']['Id']}"
-            ACCOUNT_ID, result["UserPool"]["Id"]
-        )
     )
     result["UserPool"]["Name"].should.equal(name)
     result["UserPool"]["LambdaConfig"]["PreSignUp"].should.equal(value)
@@ -847,9 +845,7 @@ def test_create_user_pool_domain_custom_domain_config():
 
     domain = str(uuid.uuid4())
     custom_domain_config = {
-        "CertificateArn": "arn:aws:acm:us-east-1:{}:certificate/123456789012".format(
+        "CertificateArn": f"arn:aws:acm:us-east-1:{ACCOUNT_ID}:certificate/123456789012"
-            ACCOUNT_ID
-        )
     }
     user_pool_id = conn.create_user_pool(PoolName=str(uuid.uuid4()))["UserPool"]["Id"]
     result = conn.create_user_pool_domain(
@@ -896,9 +892,7 @@ def test_update_user_pool_domain():
 
     domain = str(uuid.uuid4())
     custom_domain_config = {
-        "CertificateArn": "arn:aws:acm:us-east-1:{}:certificate/123456789012".format(
+        "CertificateArn": f"arn:aws:acm:us-east-1:{ACCOUNT_ID}:certificate/123456789012"
-            ACCOUNT_ID
-        )
     }
     user_pool_id = conn.create_user_pool(PoolName=str(uuid.uuid4()))["UserPool"]["Id"]
     conn.create_user_pool_domain(UserPoolId=user_pool_id, Domain=domain)
@@ -2395,7 +2389,7 @@ def test_list_users_inherent_attributes():
 
     for name, filter_value, response_field, response_field_expected_value in filters:
         result = conn.list_users(
-            UserPoolId=user_pool_id, Filter='{}="{}"'.format(name, filter_value)
+            UserPoolId=user_pool_id, Filter=f'{name}="{filter_value}"'
         )
         result["Users"].should.have.length_of(1)
         result["Users"][0][response_field].should.equal(response_field_expected_value)
@@ -2839,8 +2833,8 @@ def test_token_legitimacy():
         access_token = outputs["access_token"]
         client_id = outputs["client_id"]
         username = outputs["username"]
-        issuer = "https://cognito-idp.us-west-2.amazonaws.com/{}".format(
+        issuer = (
-            outputs["user_pool_id"]
+            f"https://cognito-idp.us-west-2.amazonaws.com/{outputs['user_pool_id']}"
         )
         id_claims = json.loads(jws.verify(id_token, json_web_key, "RS256"))
         id_claims["iss"].should.equal(issuer)
@@ -3451,7 +3445,7 @@ def test_resource_server():
     ex.value.operation_name.should.equal("CreateResourceServer")
     ex.value.response["Error"]["Code"].should.equal("InvalidParameterException")
     ex.value.response["Error"]["Message"].should.equal(
-        "%s already exists in user pool %s." % (identifier, user_pool_id)
+        f"{identifier} already exists in user pool {user_pool_id}."
     )
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
 
@@ -4308,8 +4302,6 @@ def verify_kid_header(token):
 
 
 def fetch_public_keys():
-    keys_url = "https://cognito-idp.{}.amazonaws.com/{}/.well-known/jwks.json".format(
+    keys_url = "https://cognito-idp.us-west-2.amazonaws.com/someuserpoolid/.well-known/jwks.json"
-        "us-west-2", "someuserpoolid"
-    )
     response = requests.get(keys_url).json()
     return response["keys"]

tests/test_config/test_config.py

@@ -289,9 +289,7 @@ def test_put_configuration_aggregator():
             AccountAggregationSources=[
                 {"AccountIds": ["012345678910"], "AllAwsRegions": True}
             ],
-            Tags=[
+            Tags=[{"Key": f"{x}", "Value": f"{x}"} for x in range(0, 51)],
-                {"Key": "{}".format(x), "Value": "{}".format(x)} for x in range(0, 51)
-            ],
         )
     assert (
         "Member must have length less than or equal to 50"
@@ -399,9 +397,7 @@ def test_put_configuration_aggregator():
         account_aggregation_source
     ]
     assert (
-        "arn:aws:config:us-west-2:{}:config-aggregator/config-aggregator-".format(
+        f"arn:aws:config:us-west-2:{ACCOUNT_ID}:config-aggregator/config-aggregator-"
-            ACCOUNT_ID
-        )
         in result["ConfigurationAggregator"]["ConfigurationAggregatorArn"]
     )
     assert (
@@ -455,7 +451,7 @@ def test_describe_configuration_aggregators():
     # Make 10 config aggregators:
     for x in range(0, 10):
         client.put_configuration_aggregator(
-            ConfigurationAggregatorName="testing{}".format(x),
+            ConfigurationAggregatorName=f"testing{x}",
             AccountAggregationSources=[
                 {"AccountIds": ["012345678910"], "AllAwsRegions": True}
             ],
@@ -509,19 +505,19 @@ def test_describe_configuration_aggregators():
     assert result["NextToken"] == "testing4"
     assert [
         agg["ConfigurationAggregatorName"] for agg in result["ConfigurationAggregators"]
-    ] == ["testing{}".format(x) for x in range(0, 4)]
+    ] == [f"testing{x}" for x in range(0, 4)]
     result = client.describe_configuration_aggregators(Limit=4, NextToken="testing4")
     assert len(result["ConfigurationAggregators"]) == 4
     assert result["NextToken"] == "testing8"
     assert [
         agg["ConfigurationAggregatorName"] for agg in result["ConfigurationAggregators"]
-    ] == ["testing{}".format(x) for x in range(4, 8)]
+    ] == [f"testing{x}" for x in range(4, 8)]
     result = client.describe_configuration_aggregators(Limit=4, NextToken="testing8")
     assert len(result["ConfigurationAggregators"]) == 2
     assert not result.get("NextToken")
     assert [
         agg["ConfigurationAggregatorName"] for agg in result["ConfigurationAggregators"]
-    ] == ["testing{}".format(x) for x in range(8, 10)]
+    ] == [f"testing{x}" for x in range(8, 10)]
 
     # Test Pagination with Filtering:
     result = client.describe_configuration_aggregators(
@@ -560,9 +556,7 @@ def test_put_aggregation_authorization():
         client.put_aggregation_authorization(
             AuthorizedAccountId="012345678910",
             AuthorizedAwsRegion="us-west-2",
-            Tags=[
+            Tags=[{"Key": f"{x}", "Value": f"{x}"} for x in range(0, 51)],
-                {"Key": "{}".format(x), "Value": "{}".format(x)} for x in range(0, 51)
-            ],
         )
     assert (
         "Member must have length less than or equal to 50"
@@ -626,10 +620,9 @@ def test_put_aggregation_authorization():
         Tags=[{"Key": "tag", "Value": "a"}],
     )
 
-    assert result["AggregationAuthorization"][
+    assert (
-        "AggregationAuthorizationArn"
+        result["AggregationAuthorization"]["AggregationAuthorizationArn"]
-    ] == "arn:aws:config:us-west-2:{}:aggregation-authorization/012345678910/us-east-1".format(
+        == f"arn:aws:config:us-west-2:{ACCOUNT_ID}:aggregation-authorization/012345678910/us-east-1"
-        ACCOUNT_ID
     )
     assert result["AggregationAuthorization"]["AuthorizedAccountId"] == "012345678910"
     assert result["AggregationAuthorization"]["AuthorizedAwsRegion"] == "us-east-1"
@@ -641,10 +634,9 @@ def test_put_aggregation_authorization():
     result = client.put_aggregation_authorization(
         AuthorizedAccountId="012345678910", AuthorizedAwsRegion="us-east-1"
     )
-    assert result["AggregationAuthorization"][
+    assert (
-        "AggregationAuthorizationArn"
+        result["AggregationAuthorization"]["AggregationAuthorizationArn"]
-    ] == "arn:aws:config:us-west-2:{}:aggregation-authorization/012345678910/us-east-1".format(
+        == f"arn:aws:config:us-west-2:{ACCOUNT_ID}:aggregation-authorization/012345678910/us-east-1"
-        ACCOUNT_ID
     )
     assert result["AggregationAuthorization"]["AuthorizedAccountId"] == "012345678910"
     assert result["AggregationAuthorization"]["AuthorizedAwsRegion"] == "us-east-1"
@@ -661,7 +653,7 @@ def test_describe_aggregation_authorizations():
     # Make 10 account authorizations:
     for i in range(0, 10):
         client.put_aggregation_authorization(
-            AuthorizedAccountId="{}".format(str(i) * 12),
+            AuthorizedAccountId=f"{str(i) * 12}",
             AuthorizedAwsRegion="us-west-2",
         )
 
@@ -679,7 +671,7 @@ def test_describe_aggregation_authorizations():
     assert result["NextToken"] == ("4" * 12) + "/us-west-2"
     assert [
         auth["AuthorizedAccountId"] for auth in result["AggregationAuthorizations"]
-    ] == ["{}".format(str(x) * 12) for x in range(0, 4)]
+    ] == [f"{str(x) * 12}" for x in range(0, 4)]
 
     result = client.describe_aggregation_authorizations(
         Limit=4, NextToken=("4" * 12) + "/us-west-2"
@@ -688,7 +680,7 @@ def test_describe_aggregation_authorizations():
     assert result["NextToken"] == ("8" * 12) + "/us-west-2"
     assert [
         auth["AuthorizedAccountId"] for auth in result["AggregationAuthorizations"]
-    ] == ["{}".format(str(x) * 12) for x in range(4, 8)]
+    ] == [f"{str(x) * 12}" for x in range(4, 8)]
 
     result = client.describe_aggregation_authorizations(
         Limit=4, NextToken=("8" * 12) + "/us-west-2"
@@ -697,7 +689,7 @@ def test_describe_aggregation_authorizations():
     assert not result.get("NextToken")
     assert [
         auth["AuthorizedAccountId"] for auth in result["AggregationAuthorizations"]
-    ] == ["{}".format(str(x) * 12) for x in range(8, 10)]
+    ] == [f"{str(x) * 12}" for x in range(8, 10)]
 
     # Test with an invalid filter:
     with pytest.raises(ClientError) as ce:
@@ -1252,7 +1244,7 @@ def test_list_discovered_resource():
     s3_client = boto3.client("s3", region_name="us-west-2")
     for x in range(0, 10):
         s3_client.create_bucket(
-            Bucket="bucket{}".format(x),
+            Bucket=f"bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "us-west-2"},
         )
 
@@ -1269,8 +1261,8 @@ def test_list_discovered_resource():
     for x in range(0, 10):
         assert result["resourceIdentifiers"][x] == {
             "resourceType": "AWS::S3::Bucket",
-            "resourceId": "bucket{}".format(x),
+            "resourceId": f"bucket{x}",
-            "resourceName": "bucket{}".format(x),
+            "resourceName": f"bucket{x}",
         }
     assert not result.get("nextToken")
 
@@ -1330,7 +1322,7 @@ def test_list_discovered_resource():
     )
 
     # More than 20 resourceIds:
-    resource_ids = ["{}".format(x) for x in range(0, 21)]
+    resource_ids = [f"{x}" for x in range(0, 21)]
     with pytest.raises(ClientError) as ce:
         client.list_discovered_resources(
             resourceType="AWS::S3::Bucket", resourceIds=resource_ids
@@ -1378,14 +1370,14 @@ def test_list_aggregate_discovered_resource():
     s3_client = boto3.client("s3", region_name="us-west-2")
     for x in range(0, 10):
         s3_client.create_bucket(
-            Bucket="bucket{}".format(x),
+            Bucket=f"bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "us-west-2"},
         )
 
     s3_client_eu = boto3.client("s3", region_name="eu-west-1")
     for x in range(10, 12):
         s3_client_eu.create_bucket(
-            Bucket="eu-bucket{}".format(x),
+            Bucket=f"eu-bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "eu-west-1"},
         )
 
@@ -1398,16 +1390,16 @@ def test_list_aggregate_discovered_resource():
         assert result["ResourceIdentifiers"][x] == {
             "SourceAccountId": ACCOUNT_ID,
             "ResourceType": "AWS::S3::Bucket",
-            "ResourceId": "bucket{}".format(x),
+            "ResourceId": f"bucket{x}",
-            "ResourceName": "bucket{}".format(x),
+            "ResourceName": f"bucket{x}",
             "SourceRegion": "us-west-2",
         }
     for x in range(11, 12):
         assert result["ResourceIdentifiers"][x] == {
             "SourceAccountId": ACCOUNT_ID,
             "ResourceType": "AWS::S3::Bucket",
-            "ResourceId": "eu-bucket{}".format(x),
+            "ResourceId": f"eu-bucket{x}",
-            "ResourceName": "eu-bucket{}".format(x),
+            "ResourceName": f"eu-bucket{x}",
             "SourceRegion": "eu-west-1",
         }
 
@@ -1519,7 +1511,7 @@ def test_get_resource_config_history():
     s3_client = boto3.client("s3", region_name="us-west-2")
     for x in range(0, 10):
         s3_client.create_bucket(
-            Bucket="bucket{}".format(x),
+            Bucket=f"bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "us-west-2"},
         )
 
@@ -1580,18 +1572,18 @@ def test_batch_get_resource_config():
     s3_client = boto3.client("s3", region_name="us-west-2")
     for x in range(0, 10):
         s3_client.create_bucket(
-            Bucket="bucket{}".format(x),
+            Bucket=f"bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "us-west-2"},
         )
 
     # Get them all:
     keys = [
-        {"resourceType": "AWS::S3::Bucket", "resourceId": "bucket{}".format(x)}
+        {"resourceType": "AWS::S3::Bucket", "resourceId": f"bucket{x}"}
         for x in range(0, 10)
     ]
     result = client.batch_get_resource_config(resourceKeys=keys)
     assert len(result["baseConfigurationItems"]) == 10
-    buckets_missing = ["bucket{}".format(x) for x in range(0, 10)]
+    buckets_missing = [f"bucket{x}" for x in range(0, 10)]
     for r in result["baseConfigurationItems"]:
         buckets_missing.remove(r["resourceName"])
 
@@ -1656,22 +1648,22 @@ def test_batch_get_aggregate_resource_config():
     s3_client = boto3.client("s3", region_name="us-west-2")
     for x in range(0, 10):
         s3_client.create_bucket(
-            Bucket="bucket{}".format(x),
+            Bucket=f"bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "us-west-2"},
         )
         s3_client.put_bucket_tagging(
-            Bucket="bucket{}".format(x),
+            Bucket=f"bucket{x}",
             Tagging={"TagSet": [{"Key": "Some", "Value": "Tag"}]},
         )
 
     s3_client_eu = boto3.client("s3", region_name="eu-west-1")
     for x in range(10, 12):
         s3_client_eu.create_bucket(
-            Bucket="eu-bucket{}".format(x),
+            Bucket=f"eu-bucket{x}",
             CreateBucketConfiguration={"LocationConstraint": "eu-west-1"},
         )
         s3_client.put_bucket_tagging(
-            Bucket="eu-bucket{}".format(x),
+            Bucket=f"eu-bucket{x}",
             Tagging={"TagSet": [{"Key": "Some", "Value": "Tag"}]},
         )
 
@@ -1681,7 +1673,7 @@ def test_batch_get_aggregate_resource_config():
             "SourceAccountId": ACCOUNT_ID,
             "SourceRegion": "us-west-2",
             "ResourceType": "AWS::S3::Bucket",
-            "ResourceId": "bucket{}".format(x),
+            "ResourceId": f"bucket{x}",
         }
         for x in range(0, 10)
     ]
@@ -1690,7 +1682,7 @@ def test_batch_get_aggregate_resource_config():
             "SourceAccountId": ACCOUNT_ID,
             "SourceRegion": "eu-west-1",
             "ResourceType": "AWS::S3::Bucket",
-            "ResourceId": "eu-bucket{}".format(x),
+            "ResourceId": f"eu-bucket{x}",
         }
         for x in range(10, 12)
     ]
@@ -1704,8 +1696,8 @@ def test_batch_get_aggregate_resource_config():
 
     # Verify all the buckets are there:
     assert len(result["BaseConfigurationItems"]) == 12
-    missing_buckets = ["bucket{}".format(x) for x in range(0, 10)] + [
+    missing_buckets = [f"bucket{x}" for x in range(0, 10)] + [
-        "eu-bucket{}".format(x) for x in range(10, 12)
+        f"eu-bucket{x}" for x in range(10, 12)
     ]
 
     for r in result["BaseConfigurationItems"]:
@@ -2063,7 +2055,7 @@ def test_get_organization_conformance_pack_detailed_status():
     status = response["OrganizationConformancePackDetailedStatuses"][0]
     status["AccountId"].should.equal(ACCOUNT_ID)
     status["ConformancePackName"].should.equal(
-        "OrgConformsPack-{}".format(arn[arn.rfind("/") + 1 :])
+        f"OrgConformsPack-{arn[arn.rfind('/') + 1 :]}"
     )
     status["Status"].should.equal("CREATE_SUCCESSFUL")
     update_time = status["LastUpdateTime"]
@@ -2085,7 +2077,7 @@ def test_get_organization_conformance_pack_detailed_status():
     status = response["OrganizationConformancePackDetailedStatuses"][0]
     status["AccountId"].should.equal(ACCOUNT_ID)
     status["ConformancePackName"].should.equal(
-        "OrgConformsPack-{}".format(arn[arn.rfind("/") + 1 :])
+        f"OrgConformsPack-{arn[arn.rfind('/') + 1 :]}"
     )
     status["Status"].should.equal("UPDATE_SUCCESSFUL")
     status["LastUpdateTime"].should.be.greater_than(update_time)

tests/test_core/test_auth.py

@@ -258,11 +258,7 @@ def test_access_denied_with_no_policy():
     ex.value.response["Error"]["Code"].should.equal("AccessDenied")
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(403)
     ex.value.response["Error"]["Message"].should.equal(
-        "User: arn:aws:iam::{account_id}:user/{user_name} is not authorized to perform: {operation}".format(
+        f"User: arn:aws:iam::{ACCOUNT_ID}:user/{user_name} is not authorized to perform: ec2:DescribeInstances"
-            account_id=ACCOUNT_ID,
-            user_name=user_name,
-            operation="ec2:DescribeInstances",
-        )
     )
 
 
@@ -288,11 +284,7 @@ def test_access_denied_with_not_allowing_policy():
     ex.value.response["Error"]["Code"].should.equal("AccessDenied")
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(403)
     ex.value.response["Error"]["Message"].should.equal(
-        "User: arn:aws:iam::{account_id}:user/{user_name} is not authorized to perform: {operation}".format(
+        f"User: arn:aws:iam::{ACCOUNT_ID}:user/{user_name} is not authorized to perform: ec2:DescribeInstances"
-            account_id=ACCOUNT_ID,
-            user_name=user_name,
-            operation="ec2:DescribeInstances",
-        )
     )
 
 
@@ -324,9 +316,7 @@ def test_access_denied_for_run_instances():
     ex.value.response["Error"]["Code"].should.equal("AccessDenied")
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(403)
     ex.value.response["Error"]["Message"].should.equal(
-        "User: arn:aws:iam::{account_id}:user/{user_name} is not authorized to perform: {operation}".format(
+        f"User: arn:aws:iam::{ACCOUNT_ID}:user/{user_name} is not authorized to perform: ec2:RunInstances"
-            account_id=ACCOUNT_ID, user_name=user_name, operation="ec2:RunInstances"
-        )
     )
 
 
@@ -355,9 +345,7 @@ def test_access_denied_with_denying_policy():
     ex.value.response["Error"]["Code"].should.equal("AccessDenied")
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(403)
     ex.value.response["Error"]["Message"].should.equal(
-        "User: arn:aws:iam::{account_id}:user/{user_name} is not authorized to perform: {operation}".format(
+        f"User: arn:aws:iam::{ACCOUNT_ID}:user/{user_name} is not authorized to perform: ec2:CreateVpc"
-            account_id=ACCOUNT_ID, user_name=user_name, operation="ec2:CreateVpc"
-        )
     )
 
 
@@ -535,9 +523,7 @@ def test_access_denied_with_many_irrelevant_policies():
     ex.value.response["Error"]["Code"].should.equal("AccessDenied")
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(403)
     ex.value.response["Error"]["Message"].should.equal(
-        "User: arn:aws:iam::{account_id}:user/{user_name} is not authorized to perform: {operation}".format(
+        f"User: arn:aws:iam::{ACCOUNT_ID}:user/{user_name} is not authorized to perform: ec2:CreateKeyPair"
-            account_id=ACCOUNT_ID, user_name=user_name, operation="ec2:CreateKeyPair"
-        )
     )
 
 
@@ -552,9 +538,7 @@ def test_allowed_with_temporary_credentials():
         "Version": "2012-10-17",
         "Statement": {
             "Effect": "Allow",
-            "Principal": {
+            "Principal": {"AWS": f"arn:aws:iam::{ACCOUNT_ID}:root"},
-                "AWS": "arn:aws:iam::{account_id}:root".format(account_id=ACCOUNT_ID)
-            },
             "Action": "sts:AssumeRole",
         },
     }
@@ -607,9 +591,7 @@ def test_access_denied_with_temporary_credentials():
         "Version": "2012-10-17",
         "Statement": {
             "Effect": "Allow",
-            "Principal": {
+            "Principal": {"AWS": f"arn:aws:iam::{ACCOUNT_ID}:root"},
-                "AWS": "arn:aws:iam::{account_id}:root".format(account_id=ACCOUNT_ID)
-            },
             "Action": "sts:AssumeRole",
         },
     }
@@ -638,12 +620,7 @@ def test_access_denied_with_temporary_credentials():
     ex.value.response["Error"]["Code"].should.equal("AccessDenied")
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(403)
     ex.value.response["Error"]["Message"].should.equal(
-        "User: arn:aws:sts::{account_id}:assumed-role/{role_name}/{session_name} is not authorized to perform: {operation}".format(
+        f"User: arn:aws:sts::{ACCOUNT_ID}:assumed-role/{role_name}/{session_name} is not authorized to perform: rds:CreateDBInstance"
-            account_id=ACCOUNT_ID,
-            role_name=role_name,
-            session_name=session_name,
-            operation="rds:CreateDBInstance",
-        )
     )
 
 
@@ -753,9 +730,7 @@ def test_s3_invalid_token_with_temporary_credentials():
         "Version": "2012-10-17",
         "Statement": {
             "Effect": "Allow",
-            "Principal": {
+            "Principal": {"AWS": f"arn:aws:iam::{ACCOUNT_ID}:root"},
-                "AWS": "arn:aws:iam::{account_id}:root".format(account_id=ACCOUNT_ID)
-            },
             "Action": "sts:AssumeRole",
         },
     }

tests/test_core/test_instance_metadata.py

@@ -11,13 +11,13 @@ else:
 
 @mock_ec2
 def test_latest_meta_data():
-    res = requests.get("{0}/latest/meta-data/".format(BASE_URL))
+    res = requests.get(f"{BASE_URL}/latest/meta-data/")
     res.content.should.equal(b"iam")
 
 
 @mock_ec2
 def test_meta_data_iam():
-    res = requests.get("{0}/latest/meta-data/iam".format(BASE_URL))
+    res = requests.get(f"{BASE_URL}/latest/meta-data/iam")
     json_response = res.json()
     default_role = json_response["security-credentials"]["default-role"]
     default_role.should.contain("AccessKeyId")
@@ -28,16 +28,14 @@ def test_meta_data_iam():
 
 @mock_ec2
 def test_meta_data_security_credentials():
-    res = requests.get(
+    res = requests.get(f"{BASE_URL}/latest/meta-data/iam/security-credentials/")
-        "{0}/latest/meta-data/iam/security-credentials/".format(BASE_URL)
-    )
     res.content.should.equal(b"default-role")
 
 
 @mock_ec2
 def test_meta_data_default_role():
     res = requests.get(
-        "{0}/latest/meta-data/iam/security-credentials/default-role".format(BASE_URL)
+        f"{BASE_URL}/latest/meta-data/iam/security-credentials/default-role"
     )
     json_response = res.json()
     json_response.should.contain("AccessKeyId")

tests/test_core/test_moto_api.py

@@ -21,7 +21,7 @@ def test_reset_api():
     conn.create_queue(QueueName="queue1")
     conn.list_queues()["QueueUrls"].should.have.length_of(1)
 
-    res = requests.post("{base_url}/moto-api/reset".format(base_url=base_url))
+    res = requests.post(f"{base_url}/moto-api/reset")
     res.content.should.equal(b'{"status": "ok"}')
 
     conn.list_queues().shouldnt.contain("QueueUrls")  # No more queues
@@ -32,7 +32,7 @@ def test_data_api():
     conn = boto3.client("sqs", region_name="us-west-1")
     conn.create_queue(QueueName="queue1")
 
-    res = requests.post("{base_url}/moto-api/data.json".format(base_url=base_url))
+    res = requests.post(f"{base_url}/moto-api/data.json")
     queues = res.json()["sqs"]["Queue"]
     len(queues).should.equal(1)
     queue = queues[0]

tests/test_core/test_request_mocking.py

@@ -8,7 +8,7 @@ from moto import mock_s3, mock_sts, mock_sqs, settings
 
 @mock_sqs
 @pytest.mark.network
-def test_passthrough_requests():
+def test_passthrough_requests() -> None:
     conn = boto3.client("sqs", region_name="us-west-1")
     conn.create_queue(QueueName="queue1")
 
@@ -19,7 +19,7 @@ def test_passthrough_requests():
 if not settings.TEST_SERVER_MODE:
 
     @mock_sqs
-    def test_requests_to_amazon_subdomains_dont_work():
+    def test_requests_to_amazon_subdomains_dont_work() -> None:
         res = requests.get("https://fakeservice.amazonaws.com/foo/bar")
         assert res.content == b"The method is not implemented"
         assert res.status_code == 400
@@ -27,7 +27,7 @@ if not settings.TEST_SERVER_MODE:
 
 @mock_sts
 @mock_s3
-def test_decorator_ordering():
+def test_decorator_ordering() -> None:
     """
     https://github.com/spulec/moto/issues/3790#issuecomment-803979809
     """
@@ -49,4 +49,4 @@ def test_decorator_ordering():
     )
 
     resp = requests.get(presigned_url)
-    resp.status_code.should.equal(200)
+    resp.status_code.should.equal(200)  # type: ignore[attr-defined]

tests/test_core/test_url_base_regex.py

@@ -19,11 +19,11 @@ class TestMockBucketStartingWithServiceName:
     @pytest.mark.parametrize("service_name,decorator", service_names)
     def test_bucketname_starting_with_service_name(self, service_name, decorator):
 
-        decorator = getattr(moto, "mock_{}".format(service_name))
+        decorator = getattr(moto, f"mock_{service_name}")
         with decorator():
             with mock_s3():
                 s3_client = boto3.client("s3", "eu-west-1")
-                bucket_name = "{}-bucket".format(service_name)
+                bucket_name = f"{service_name}-bucket"
                 s3_client.create_bucket(
                     ACL="private",
                     Bucket=bucket_name,

tests/test_datapipeline/test_datapipeline.py

@@ -157,7 +157,7 @@ def test_listing_pipelines_boto3():
 def test_listing_paginated_pipelines_boto3():
     conn = boto3.client("datapipeline", region_name="us-west-2")
     for i in range(100):
-        conn.create_pipeline(name="mypipeline%d" % i, uniqueId="some-unique-id%d" % i)
+        conn.create_pipeline(name=f"mypipeline{i}", uniqueId=f"some-unique-id{i}")
 
     response = conn.list_pipelines()
 

tests/test_dynamodb/test_dynamodb.py

@@ -145,7 +145,7 @@ def test_list_table_tags_paginated():
     table_description = conn.describe_table(TableName=name)
     arn = table_description["Table"]["TableArn"]
     for i in range(11):
-        tags = [{"Key": "TestTag%d" % i, "Value": "TestValue"}]
+        tags = [{"Key": f"TestTag{i}", "Value": "TestValue"}]
         conn.tag_resource(ResourceArn=arn, Tags=tags)
     resp = conn.list_tags_of_resource(ResourceArn=arn)
     assert len(resp["Tags"]) == 10
@@ -3861,7 +3861,7 @@ def test_transact_write_items_put_conditional_expressions():
                 {
                     "Put": {
                         "Item": {
-                            "id": {"S": "foo{}".format(str(i))},
+                            "id": {"S": f"foo{i}"},
                             "foo": {"S": "bar"},
                         },
                         "TableName": "test-table",
@@ -4285,9 +4285,7 @@ def assert_correct_client_error(
     braces = braces or ["{", "}"]
     assert client_error.response["Error"]["Code"] == code
     if message_values is not None:
-        values_string = "{open_brace}(?P<values>.*){close_brace}".format(
+        values_string = f"{braces[0]}(?P<values>.*){braces[1]}"
-            open_brace=braces[0], close_brace=braces[1]
-        )
         re_msg = re.compile(message_template.format(values=values_string))
         match_result = re_msg.match(client_error.response["Error"]["Message"])
         assert match_result is not None
@@ -4886,7 +4884,7 @@ def test_set_attribute_is_dropped_if_empty_after_update_expression(attr_name):
     client.update_item(
         TableName=table_name,
         Key={"customer": {"S": item_key}},
-        UpdateExpression="ADD {} :order".format(attr_name),
+        UpdateExpression=f"ADD {attr_name} :order",
         ExpressionAttributeNames=expression_attribute_names,
         ExpressionAttributeValues={":order": {"SS": [set_item]}},
     )
@@ -4898,7 +4896,7 @@ def test_set_attribute_is_dropped_if_empty_after_update_expression(attr_name):
     client.update_item(
         TableName=table_name,
         Key={"customer": {"S": item_key}},
-        UpdateExpression="DELETE {} :order".format(attr_name),
+        UpdateExpression=f"DELETE {attr_name} :order",
         ExpressionAttributeNames=expression_attribute_names,
         ExpressionAttributeValues={":order": {"SS": [set_item]}},
     )
@@ -5193,7 +5191,7 @@ def test_describe_backup_for_non_existent_backup_raises_error():
         client.describe_backup(BackupArn=non_existent_arn)
     error = ex.value.response["Error"]
     error["Code"].should.equal("BackupNotFoundException")
-    error["Message"].should.equal("Backup not found: {}".format(non_existent_arn))
+    error["Message"].should.equal(f"Backup not found: {non_existent_arn}")
 
 
 @mock_dynamodb
@@ -5280,7 +5278,7 @@ def test_restore_table_from_non_existent_backup_raises_error():
         )
     error = ex.value.response["Error"]
     error["Code"].should.equal("BackupNotFoundException")
-    error["Message"].should.equal("Backup not found: {}".format(non_existent_arn))
+    error["Message"].should.equal(f"Backup not found: {non_existent_arn}")
 
 
 @mock_dynamodb
@@ -5301,7 +5299,7 @@ def test_restore_table_from_backup_raises_error_when_table_already_exists():
         )
     error = ex.value.response["Error"]
     error["Code"].should.equal("TableAlreadyExistsException")
-    error["Message"].should.equal("Table already exists: {}".format(table_name))
+    error["Message"].should.equal(f"Table already exists: {table_name}")
 
 
 @mock_dynamodb
@@ -5316,7 +5314,7 @@ def test_restore_table_from_backup():
     )
     table = resp.get("TableDescription")
     for i in range(5):
-        client.put_item(TableName=table_name, Item={"id": {"S": "item %d" % i}})
+        client.put_item(TableName=table_name, Item={"id": {"S": f"item {i}"}})
 
     backup_arn = (
         client.create_backup(TableName=table_name, BackupName="backup")
@@ -5356,7 +5354,7 @@ def test_restore_table_to_point_in_time():
     )
     table = resp.get("TableDescription")
     for i in range(5):
-        client.put_item(TableName=table_name, Item={"id": {"S": "item %d" % i}})
+        client.put_item(TableName=table_name, Item={"id": {"S": f"item {i}"}})
 
     restored_table_name = "restored-from-pit"
     restored = client.restore_table_to_point_in_time(
@@ -5385,7 +5383,7 @@ def test_restore_table_to_point_in_time_raises_error_when_source_not_exist():
         )
     error = ex.value.response["Error"]
     error["Code"].should.equal("SourceTableNotFoundException")
-    error["Message"].should.equal("Source table not found: %s" % table_name)
+    error["Message"].should.equal(f"Source table not found: {table_name}")
 
 
 @mock_dynamodb
@@ -5411,7 +5409,7 @@ def test_restore_table_to_point_in_time_raises_error_when_dest_exist():
         )
     error = ex.value.response["Error"]
     error["Code"].should.equal("TableAlreadyExistsException")
-    error["Message"].should.equal("Table already exists: %s" % restored_table_name)
+    error["Message"].should.equal(f"Table already exists: {restored_table_name}")
 
 
 @mock_dynamodb
@@ -5422,7 +5420,7 @@ def test_delete_non_existent_backup_raises_error():
         client.delete_backup(BackupArn=non_existent_arn)
     error = ex.value.response["Error"]
     error["Code"].should.equal("BackupNotFoundException")
-    error["Message"].should.equal("Backup not found: {}".format(non_existent_arn))
+    error["Message"].should.equal(f"Backup not found: {non_existent_arn}")
 
 
 @mock_dynamodb
@@ -5511,7 +5509,7 @@ def test_describe_endpoints(region):
     res.should.equal(
         [
             {
-                "Address": "dynamodb.{}.amazonaws.com".format(region),
+                "Address": f"dynamodb.{region}.amazonaws.com",
                 "CachePeriodInMinutes": 1440,
             },
         ]

tests/test_dynamodb/test_dynamodb_executor.py

@@ -253,7 +253,7 @@ def test_execution_of_remove_in_list(table):
 @pytest.mark.parametrize("attr_name", ["s", "#placeholder"])
 def test_execution_of_delete_element_from_set(table, attr_name):
     expression_attribute_names = {"#placeholder": "s"}
-    update_expression = "delete {} :value".format(attr_name)
+    update_expression = f"delete {attr_name} :value"
     update_expression_ast = UpdateExpressionParser.make(update_expression)
     item = Item(
         hash_key=DynamoType({"S": "id"}),
@@ -276,7 +276,7 @@ def test_execution_of_delete_element_from_set(table, attr_name):
     assert expected_item == item
 
     # delete last elements
-    update_expression = "delete {} :value".format(attr_name)
+    update_expression = f"delete {attr_name} :value"
     update_expression_ast = UpdateExpressionParser.make(update_expression)
     validated_ast = UpdateExpressionValidator(
         update_expression_ast,

tests/test_dynamodb/test_dynamodb_table_with_range_key.py

@@ -192,9 +192,7 @@ def test_boto3_conditions_ignorecase():
     for expr in between_expressions:
         results = dynamodb.query(
             TableName="users",
-            KeyConditionExpression="forum_name = :forum_name and subject {}".format(
+            KeyConditionExpression=f"forum_name = :forum_name and subject {expr}",
-                expr
-            ),
             ExpressionAttributeValues={
                 ":forum_name": {"S": "the-key"},
                 ":start": {"S": "100"},
@@ -1023,7 +1021,7 @@ def test_query_pagination():
         table.put_item(
             Item={
                 "forum_name": "the-key",
-                "subject": "{0}".format(i),
+                "subject": f"{i}",
                 "username": "johndoe",
                 "created": Decimal("3"),
             }

tests/test_dynamodb/test_dynamodb_table_without_range_key.py

@@ -505,7 +505,7 @@ def test_update_settype_item_with_conditions():
 def test_scan_pagination():
     table = _create_user_table()
 
-    expected_usernames = ["user{0}".format(i) for i in range(10)]
+    expected_usernames = [f"user{i}" for i in range(10)]
     for u in expected_usernames:
         table.put_item(Item={"username": u})
 

tests/test_dynamodb_v20111205/test_server.py

@@ -1319,7 +1319,7 @@ def create_table(test_client, name=None, region=None, use_range_key=True):
         "Content-Type": "application/x-amz-json-1.0",
     }
     if region:
-        headers["Host"] = "dynamodb.{}.amazonaws.com".format(region)
+        headers["Host"] = f"dynamodb.{region}.amazonaws.com"
     request_body = {
         "TableName": name,
         "KeySchema": {

tests/test_ec2/test_amis.py

@@ -599,8 +599,8 @@ def test_ami_attribute_user_permissions():
     ]
     permissions.should.equal([])
 
-    USER1 = "".join(["{}".format(random.randint(0, 9)) for _ in range(0, 12)])
+    USER1 = "".join([f"{random.randint(0, 9)}" for _ in range(0, 12)])
-    USER2 = "".join(["{}".format(random.randint(0, 9)) for _ in range(0, 12)])
+    USER2 = "".join([f"{random.randint(0, 9)}" for _ in range(0, 12)])
 
     ADD_USERS_ARGS = {
         "ImageId": image.id,
@@ -673,7 +673,7 @@ def test_ami_describe_executable_users():
     instance_id = response["Reservations"][0]["Instances"][0]["InstanceId"]
     image_id = conn.create_image(InstanceId=instance_id, Name="TestImage")["ImageId"]
 
-    USER1 = "".join(["{}".format(random.randint(0, 9)) for _ in range(0, 12)])
+    USER1 = "".join([f"{random.randint(0, 9)}" for _ in range(0, 12)])
 
     ADD_USER_ARGS = {
         "ImageId": image_id,
@@ -706,8 +706,8 @@ def test_ami_describe_executable_users_negative():
     instance_id = response["Reservations"][0]["Instances"][0]["InstanceId"]
     image_id = conn.create_image(InstanceId=instance_id, Name="TestImage")["ImageId"]
 
-    USER1 = "".join(["{}".format(random.randint(0, 9)) for _ in range(0, 12)])
+    USER1 = "".join([f"{random.randint(0, 9)}" for _ in range(0, 12)])
-    USER2 = "".join(["{}".format(random.randint(0, 9)) for _ in range(0, 12)])
+    USER2 = "".join([f"{random.randint(0, 9)}" for _ in range(0, 12)])
 
     ADD_USER_ARGS = {
         "ImageId": image_id,
@@ -742,7 +742,7 @@ def test_ami_describe_executable_users_and_filter():
         "ImageId"
     ]
 
-    USER1 = "".join(["{}".format(random.randint(0, 9)) for _ in range(0, 12)])
+    USER1 = "".join([f"{random.randint(0, 9)}" for _ in range(0, 12)])
 
     ADD_USER_ARGS = {
         "ImageId": image_id,
@@ -1127,7 +1127,7 @@ def test_ami_filter_by_empty_tag():
     for i in range(10):
         image = client.create_image(
             InstanceId=instance.instance_id,
-            Name="MyAMI{}".format(i),
+            Name=f"MyAMI{i}",
             Description="Test",
         )
 

tests/test_ec2/test_elastic_block_store.py

@@ -107,9 +107,7 @@ def test_delete_attached_volume():
     ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.value.response["Error"]["Code"].should.equal("VolumeInUse")
     ex.value.response["Error"]["Message"].should.equal(
-        "Volume {0} is currently attached to {1}".format(
+        f"Volume {volume.id} is currently attached to {instance['InstanceId']}"
-            volume.id, instance["InstanceId"]
-        )
     )
 
     volume.detach_from_instance(InstanceId=instance["InstanceId"])

tests/test_ec2/test_instances.py

@@ -228,9 +228,7 @@ def test_instance_detach_volume_wrong_path():
         ex.value.response["Error"]["Code"].should.equal("InvalidAttachment.NotFound")
         ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
         ex.value.response["Error"]["Message"].should.equal(
-            "The volume {0} is not attached to instance {1} as device {2}".format(
+            f"The volume {volume.volume_id} is not attached to instance {instance.instance_id} as device /dev/sdf"
-                volume.volume_id, instance.instance_id, "/dev/sdf"
-            )
         )
 
 
@@ -2120,9 +2118,7 @@ def test_describe_instance_attribute():
             )
         ex.value.response["Error"]["Code"].should.equal("InvalidParameterValue")
         ex.value.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
-        message = "Value ({invalid_instance_attribute}) for parameter attribute is invalid. Unknown attribute.".format(
+        message = f"Value ({invalid_instance_attribute}) for parameter attribute is invalid. Unknown attribute."
-            invalid_instance_attribute=invalid_instance_attribute
-        )
         ex.value.response["Error"]["Message"].should.equal(message)
 
 
@@ -2227,7 +2223,7 @@ def test_instance_termination_protection():
     error = ex.value.response["Error"]
     error["Code"].should.equal("OperationNotPermitted")
     ex.value.response["Error"]["Message"].should.match(
-        r"The instance '{}' may not be terminated.*$".format(instance_id)
+        rf"The instance '{instance_id}' may not be terminated.*$"
     )
 
     # Use alternate request syntax for setting attribute.

tests/test_ec2/test_network_acls.py

@@ -304,9 +304,7 @@ def test_duplicate_network_acl_entry():
         )
     str(ex.value).should.equal(
         "An error occurred (NetworkAclEntryAlreadyExists) when calling the CreateNetworkAclEntry "
-        "operation: The network acl entry identified by {} already exists.".format(
+        f"operation: The network acl entry identified by {rule_number} already exists."
-            rule_number
-        )
     )
 
 

tests/test_ec2/test_prefix_lists.py

@@ -15,9 +15,7 @@ def test_create():
     prefix_list.should.have.key("AddressFamily").equals("?")
     prefix_list.should.have.key("State").equals("create-complete")
     prefix_list.should.have.key("PrefixListArn").equals(
-        "arn:aws:ec2:us-west-1:{}:prefix-list/{}".format(
+        f"arn:aws:ec2:us-west-1:{ACCOUNT_ID}:prefix-list/{prefix_list['PrefixListId']}"
-            ACCOUNT_ID, prefix_list["PrefixListId"]
-        )
     )
     prefix_list.should.have.key("PrefixListName").equals("examplelist")
     prefix_list.should.have.key("MaxEntries").equals(2)

tests/test_ec2/test_regions.py

@@ -63,10 +63,10 @@ def test_add_servers_to_multiple_regions_boto3():
 def test_create_autoscaling_group_boto3():
     regions = [("us-east-1", "c"), ("ap-northeast-1", "a")]
     for region, zone in regions:
-        a_zone = "{}{}".format(region, zone)
+        a_zone = f"{region}{zone}"
-        asg_name = "{}_tester_group_{}".format(region, str(uuid4())[0:6])
+        asg_name = f"{region}_tester_group_{str(uuid4())[0:6]}"
-        lb_name = "{}_lb_{}".format(region, str(uuid4())[0:6])
+        lb_name = f"{region}_lb_{str(uuid4())[0:6]}"
-        config_name = "{}_tester_{}".format(region, str(uuid4())[0:6])
+        config_name = f"{region}_tester_{str(uuid4())[0:6]}"
 
         elb_client = boto3.client("elb", region_name=region)
         elb_client.create_load_balancer(

tests/test_ec2/test_route_tables.py

@@ -818,9 +818,7 @@ def test_create_route_with_invalid_destination_cidr_block_parameter():
         )
     str(ex.value).should.equal(
         "An error occurred (InvalidParameterValue) when calling the CreateRoute "
-        "operation: Value ({}) for parameter destinationCidrBlock is invalid. This is not a valid CIDR block.".format(
+        f"operation: Value ({destination_cidr_block}) for parameter destinationCidrBlock is invalid. This is not a valid CIDR block."
-            destination_cidr_block
-        )
     )
 
     route_table.create_route(

tests/test_ec2/test_security_groups.py

@@ -589,7 +589,7 @@ def test_sec_group_rule_limit(use_vpc):
         ip_permissions = [
             {
                 "IpProtocol": "-1",
-                "IpRanges": [{"CidrIp": "{}.0.0.0/0".format(i)} for i in range(110)],
+                "IpRanges": [{"CidrIp": f"{i}.0.0.0/0"} for i in range(110)],
             }
         ]
         client.authorize_security_group_ingress(
@@ -621,7 +621,7 @@ def test_sec_group_rule_limit(use_vpc):
     permissions = [
         {
             "IpProtocol": "-1",
-            "IpRanges": [{"CidrIp": "{}.0.0.0/0".format(i)} for i in range(limit - 1)],
+            "IpRanges": [{"CidrIp": f"{i}.0.0.0/0"} for i in range(limit - 1)],
         }
     ]
     client.authorize_security_group_ingress(GroupId=sg.id, IpPermissions=permissions)
@@ -654,9 +654,7 @@ def test_sec_group_rule_limit(use_vpc):
     permissions = [
         {
             "IpProtocol": "-1",
-            "IpRanges": [
+            "IpRanges": [{"CidrIp": f"{i}.0.0.0/0"} for i in range(1, limit - 1)],
-                {"CidrIp": "{}.0.0.0/0".format(i)} for i in range(1, limit - 1)
-            ],
         }
     ]
     client.authorize_security_group_egress(GroupId=sg.id, IpPermissions=permissions)
@@ -1187,7 +1185,7 @@ def test_update_security_group_rule_descriptions_ingress():
 def test_non_existent_security_group_raises_error_on_authorize():
     client = boto3.client("ec2", "us-east-1")
     non_existent_sg = "sg-123abc"
-    expected_error = "The security group '{}' does not exist".format(non_existent_sg)
+    expected_error = f"The security group '{non_existent_sg}' does not exist"
     authorize_funcs = [
         client.authorize_security_group_egress,
         client.authorize_security_group_ingress,

tests/test_ec2/test_spot_fleet.py

@@ -22,7 +22,7 @@ def spot_config(subnet_id, allocation_strategy="lowestPrice"):
         "ClientToken": "string",
         "SpotPrice": "0.12",
         "TargetCapacity": 6,
-        "IamFleetRole": "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID),
+        "IamFleetRole": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet",
         "LaunchSpecifications": [
             {
                 "ImageId": EXAMPLE_AMI_ID,
@@ -47,9 +47,7 @@ def spot_config(subnet_id, allocation_strategy="lowestPrice"):
                 ],
                 "Monitoring": {"Enabled": True},
                 "SubnetId": subnet_id,
-                "IamInstanceProfile": {
+                "IamInstanceProfile": {"Arn": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"},
-                    "Arn": "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID)
-                },
                 "EbsOptimized": False,
                 "WeightedCapacity": 2.0,
                 "SpotPrice": "0.13",
@@ -62,9 +60,7 @@ def spot_config(subnet_id, allocation_strategy="lowestPrice"):
                 "InstanceType": "t2.large",
                 "Monitoring": {"Enabled": True},
                 "SubnetId": subnet_id,
-                "IamInstanceProfile": {
+                "IamInstanceProfile": {"Arn": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"},
-                    "Arn": "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID)
-                },
                 "EbsOptimized": False,
                 "WeightedCapacity": 4.0,
                 "SpotPrice": "10.00",
@@ -96,7 +92,7 @@ def test_create_spot_fleet_with_lowest_price():
     spot_fleet_config["SpotPrice"].should.equal("0.12")
     spot_fleet_config["TargetCapacity"].should.equal(6)
     spot_fleet_config["IamFleetRole"].should.equal(
-        "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"
     )
     spot_fleet_config["AllocationStrategy"].should.equal("lowestPrice")
     spot_fleet_config["FulfilledCapacity"].should.equal(6.0)
@@ -107,7 +103,7 @@ def test_create_spot_fleet_with_lowest_price():
     launch_spec["EbsOptimized"].should.equal(False)
     launch_spec["SecurityGroups"].should.equal([{"GroupId": "sg-123"}])
     launch_spec["IamInstanceProfile"].should.equal(
-        {"Arn": "arn:aws:iam::{}:role/fleet".format(ACCOUNT_ID)}
+        {"Arn": f"arn:aws:iam::{ACCOUNT_ID}:role/fleet"}
     )
     launch_spec["ImageId"].should.equal(EXAMPLE_AMI_ID)
     launch_spec["InstanceType"].should.equal("t2.small")

tests/test_ec2/test_subnets.py

@@ -356,11 +356,7 @@ def test_create_subnet_response_fields():
     subnet.should.have.key("AssignIpv6AddressOnCreation").which.should.equal(False)
     subnet.should.have.key("Ipv6Native").which.should.equal(False)
 
-    subnet_arn = "arn:aws:ec2:{region}:{owner_id}:subnet/{subnet_id}".format(
+    subnet_arn = f"arn:aws:ec2:{subnet['AvailabilityZone'][0:-1]}:{subnet['OwnerId']}:subnet/{subnet['SubnetId']}"
-        region=subnet["AvailabilityZone"][0:-1],
-        owner_id=subnet["OwnerId"],
-        subnet_id=subnet["SubnetId"],
-    )
     subnet.should.have.key("SubnetArn").which.should.equal(subnet_arn)
     subnet.should.have.key("Ipv6CidrBlockAssociationSet").which.should.equal([])
 
@@ -393,11 +389,7 @@ def test_describe_subnet_response_fields():
     subnet.should.have.key("AssignIpv6AddressOnCreation").which.should.equal(False)
     subnet.should.have.key("Ipv6Native").which.should.equal(False)
 
-    subnet_arn = "arn:aws:ec2:{region}:{owner_id}:subnet/{subnet_id}".format(
+    subnet_arn = f"arn:aws:ec2:{subnet['AvailabilityZone'][0:-1]}:{subnet['OwnerId']}:subnet/{subnet['SubnetId']}"
-        region=subnet["AvailabilityZone"][0:-1],
-        owner_id=subnet["OwnerId"],
-        subnet_id=subnet["SubnetId"],
-    )
     subnet.should.have.key("SubnetArn").which.should.equal(subnet_arn)
     subnet.should.have.key("Ipv6CidrBlockAssociationSet").which.should.equal([])
 
@@ -418,9 +410,7 @@ def test_create_subnet_with_invalid_availability_zone():
         )
     assert str(ex.value).startswith(
         "An error occurred (InvalidParameterValue) when calling the CreateSubnet "
-        "operation: Value ({}) for parameter availabilityZone is invalid. Subnets can currently only be created in the following availability zones: ".format(
+        f"operation: Value ({subnet_availability_zone}) for parameter availabilityZone is invalid. Subnets can currently only be created in the following availability zones: "
-            subnet_availability_zone
-        )
     )
 
 
@@ -437,7 +427,7 @@ def test_create_subnet_with_invalid_cidr_range():
         ec2.create_subnet(VpcId=vpc.id, CidrBlock=subnet_cidr_block)
     str(ex.value).should.equal(
         "An error occurred (InvalidSubnet.Range) when calling the CreateSubnet "
-        "operation: The CIDR '{}' is invalid.".format(subnet_cidr_block)
+        f"operation: The CIDR '{subnet_cidr_block}' is invalid."
     )
 
 
@@ -455,7 +445,7 @@ def test_create_subnet_with_invalid_cidr_range_multiple_vpc_cidr_blocks():
         ec2.create_subnet(VpcId=vpc.id, CidrBlock=subnet_cidr_block)
     str(ex.value).should.equal(
         "An error occurred (InvalidSubnet.Range) when calling the CreateSubnet "
-        "operation: The CIDR '{}' is invalid.".format(subnet_cidr_block)
+        f"operation: The CIDR '{subnet_cidr_block}' is invalid."
     )
 
 
@@ -472,9 +462,7 @@ def test_create_subnet_with_invalid_cidr_block_parameter():
         ec2.create_subnet(VpcId=vpc.id, CidrBlock=subnet_cidr_block)
     str(ex.value).should.equal(
         "An error occurred (InvalidParameterValue) when calling the CreateSubnet "
-        "operation: Value ({}) for parameter cidrBlock is invalid. This is not a valid CIDR block.".format(
+        f"operation: Value ({subnet_cidr_block}) for parameter cidrBlock is invalid. This is not a valid CIDR block."
-            subnet_cidr_block
-        )
     )
 
 
@@ -532,9 +520,7 @@ def test_create_subnets_with_overlapping_cidr_blocks():
         ec2.create_subnet(VpcId=vpc.id, CidrBlock=subnet_cidr_block)
     str(ex.value).should.equal(
         "An error occurred (InvalidSubnet.Conflict) when calling the CreateSubnet "
-        "operation: The CIDR '{}' conflicts with another subnet".format(
+        f"operation: The CIDR '{subnet_cidr_block}' conflicts with another subnet"
-            subnet_cidr_block
-        )
     )
 
 

tests/test_ec2/test_tags.py

@@ -131,7 +131,7 @@ def test_tag_limit_exceeded():
     instance = ec2.create_instances(ImageId=EXAMPLE_AMI_ID, MinCount=1, MaxCount=1)[0]
     tag_list = []
     for i in range(51):
-        tag_list.append({"Key": "{0:02d}".format(i + 1), "Value": ""})
+        tag_list.append({"Key": f"{i+1:02d}", "Value": ""})
 
     with pytest.raises(ClientError) as ex:
         client.create_tags(Resources=[instance.id], Tags=tag_list)

tests/test_ec2/test_transit_gateway.py

@@ -48,9 +48,7 @@ def test_create_transit_gateway():
     gateways.should.have.length_of(1)
     gateways[0].should.have.key("CreationTime")
     gateways[0].should.have.key("TransitGatewayArn").equal(
-        "arn:aws:ec2:us-east-1:{}:transit-gateway/{}".format(
+        f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/{gateway['TransitGatewayId']}"
-            ACCOUNT_ID, gateway["TransitGatewayId"]
-        )
     )
     gateways[0]["Options"].should.have.key("AssociationDefaultRouteTableId").equal(
         gateways[0]["Options"]["PropagationDefaultRouteTableId"]

tests/test_ec2/test_vpc_peering.py

@@ -399,9 +399,9 @@ def test_vpc_peering_connections_cross_region_accept_wrong_region():
         ec2_usw1.accept_vpc_peering_connection(VpcPeeringConnectionId=vpc_pcx_usw1.id)
     cm.value.response["Error"]["Code"].should.equal("OperationNotPermitted")
     exp_msg = (
-        "Incorrect region ({0}) specified for this request.VPC "
+        "Incorrect region (us-west-1) specified for this request.VPC "
-        "peering connection {1} must be "
+        f"peering connection {vpc_pcx_usw1.id} must be "
-        "accepted in region {2}".format("us-west-1", vpc_pcx_usw1.id, "ap-northeast-1")
+        "accepted in region ap-northeast-1"
     )
     cm.value.response["Error"]["Message"].should.equal(exp_msg)
 
@@ -424,9 +424,9 @@ def test_vpc_peering_connections_cross_region_reject_wrong_region():
         ec2_usw1.reject_vpc_peering_connection(VpcPeeringConnectionId=vpc_pcx_usw1.id)
     cm.value.response["Error"]["Code"].should.equal("OperationNotPermitted")
     exp_msg = (
-        "Incorrect region ({0}) specified for this request.VPC "
+        "Incorrect region (us-west-1) specified for this request.VPC "
-        "peering connection {1} must be accepted or "
+        f"peering connection {vpc_pcx_usw1.id} must be accepted or "
-        "rejected in region {2}".format("us-west-1", vpc_pcx_usw1.id, "ap-northeast-1")
+        "rejected in region ap-northeast-1"
     )
     cm.value.response["Error"]["Message"].should.equal(exp_msg)
 

tests/test_ec2/test_vpcs.py

@@ -561,14 +561,12 @@ def test_associate_vpc_ipv4_cidr_block():
     # Associate/Extend vpc CIDR range up to 5 ciders
     for i in range(43, 47):
         response = ec2.meta.client.associate_vpc_cidr_block(
-            VpcId=vpc.id, CidrBlock="10.10.{}.0/24".format(i)
+            VpcId=vpc.id, CidrBlock=f"10.10.{i}.0/24"
         )
         response["CidrBlockAssociation"]["CidrBlockState"]["State"].should.equal(
             "associating"
         )
-        response["CidrBlockAssociation"]["CidrBlock"].should.equal(
+        response["CidrBlockAssociation"]["CidrBlock"].should.equal(f"10.10.{i}.0/24")
-            "10.10.{}.0/24".format(i)
-        )
         response["CidrBlockAssociation"]["AssociationId"].should.contain(
             "vpc-cidr-assoc"
         )
@@ -590,9 +588,7 @@ def test_associate_vpc_ipv4_cidr_block():
         )
     str(ex.value).should.equal(
         "An error occurred (CidrLimitExceeded) when calling the AssociateVpcCidrBlock "
-        "operation: This network '{}' has met its maximum number of allowed CIDRs: 5".format(
+        f"operation: This network '{vpc.id}' has met its maximum number of allowed CIDRs: 5"
-            vpc.id
-        )
     )
 
 
@@ -657,8 +653,8 @@ def test_disassociate_vpc_ipv4_cidr_block():
         )
     str(ex.value).should.equal(
         "An error occurred (OperationNotPermitted) when calling the DisassociateVpcCidrBlock operation: "
-        "The vpc CIDR block with association ID {} may not be disassociated. It is the primary "
+        f"The vpc CIDR block with association ID {vpc_base_cidr_assoc_id} may not be disassociated. It is the primary "
-        "IPv4 CIDR block of the VPC".format(vpc_base_cidr_assoc_id)
+        "IPv4 CIDR block of the VPC"
     )
 
 
@@ -738,9 +734,7 @@ def test_vpc_associate_ipv6_cidr_block():
         )
     str(ex.value).should.equal(
         "An error occurred (CidrLimitExceeded) when calling the AssociateVpcCidrBlock "
-        "operation: This network '{}' has met its maximum number of allowed CIDRs: 1".format(
+        f"operation: This network '{vpc.id}' has met its maximum number of allowed CIDRs: 1"
-            vpc.id
-        )
     )
 
     # Test associate ipv6 cidr block after vpc created
@@ -848,9 +842,7 @@ def test_create_vpc_with_invalid_cidr_block_parameter():
         ec2.create_vpc(CidrBlock=vpc_cidr_block)
     str(ex.value).should.equal(
         "An error occurred (InvalidParameterValue) when calling the CreateVpc "
-        "operation: Value ({}) for parameter cidrBlock is invalid. This is not a valid CIDR block.".format(
+        f"operation: Value ({vpc_cidr_block}) for parameter cidrBlock is invalid. This is not a valid CIDR block."
-            vpc_cidr_block
-        )
     )
 
 
@@ -863,7 +855,7 @@ def test_create_vpc_with_invalid_cidr_range():
         ec2.create_vpc(CidrBlock=vpc_cidr_block)
     str(ex.value).should.equal(
         "An error occurred (InvalidVpc.Range) when calling the CreateVpc "
-        "operation: The CIDR '{}' is invalid.".format(vpc_cidr_block)
+        f"operation: The CIDR '{vpc_cidr_block}' is invalid."
     )
 
 

tests/test_ecr/test_ecr_boto3.py

@@ -22,8 +22,8 @@ from moto.core import DEFAULT_ACCOUNT_ID as ACCOUNT_ID
 
 def _create_image_digest(contents=None):
     if not contents:
-        contents = "docker_image{0}".format(int(random() * 10**6))
+        contents = f"docker_image{int(random() * 10**6)}"
-    return "sha256:%s" % hashlib.sha256(contents.encode("utf-8")).hexdigest()
+    return "sha256:" + hashlib.sha256(contents.encode("utf-8")).hexdigest()
 
 
 def _create_image_manifest():

tests/test_ecs/test_ecs_account_settings.py

@@ -130,7 +130,7 @@ def test_put_account_setting_changes_service_arn():
     response = client.list_services(cluster="dummy-cluster", launchType="FARGATE")
     service_arn = response["serviceArns"][0]
     service_arn.should.equal(
-        "arn:aws:ecs:eu-west-1:{}:service/test-ecs-service".format(ACCOUNT_ID)
+        f"arn:aws:ecs:eu-west-1:{ACCOUNT_ID}:service/test-ecs-service"
     )
 
     # Second invocation returns long ARN's by default, after deleting the preference
@@ -138,9 +138,7 @@ def test_put_account_setting_changes_service_arn():
     response = client.list_services(cluster="dummy-cluster", launchType="FARGATE")
     service_arn = response["serviceArns"][0]
     service_arn.should.equal(
-        "arn:aws:ecs:eu-west-1:{}:service/dummy-cluster/test-ecs-service".format(
+        f"arn:aws:ecs:eu-west-1:{ACCOUNT_ID}:service/dummy-cluster/test-ecs-service"
-            ACCOUNT_ID
-        )
     )
 
 

tests/test_ecs/test_ecs_boto3.py

@@ -30,7 +30,7 @@ def test_create_cluster():
     response = client.create_cluster(clusterName="test_ecs_cluster")
     response["cluster"]["clusterName"].should.equal("test_ecs_cluster")
     response["cluster"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["cluster"]["status"].should.equal("ACTIVE")
     response["cluster"]["registeredContainerInstancesCount"].should.equal(0)
@@ -60,10 +60,10 @@ def test_list_clusters():
     _ = client.create_cluster(clusterName="test_cluster1")
     response = client.list_clusters()
     response["clusterArns"].should.contain(
-        "arn:aws:ecs:us-east-2:{}:cluster/test_cluster0".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-2:{ACCOUNT_ID}:cluster/test_cluster0"
     )
     response["clusterArns"].should.contain(
-        "arn:aws:ecs:us-east-2:{}:cluster/test_cluster1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-2:{ACCOUNT_ID}:cluster/test_cluster1"
     )
 
 
@@ -104,7 +104,7 @@ def test_describe_clusters_missing():
     response = client.describe_clusters(clusters=["some-cluster"])
     response["failures"].should.contain(
         {
-            "arn": "arn:aws:ecs:us-east-1:{}:cluster/some-cluster".format(ACCOUNT_ID),
+            "arn": f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/some-cluster",
             "reason": "MISSING",
         }
     )
@@ -117,7 +117,7 @@ def test_delete_cluster():
     response = client.delete_cluster(cluster="test_ecs_cluster")
     response["cluster"]["clusterName"].should.equal("test_ecs_cluster")
     response["cluster"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["cluster"]["status"].should.equal("ACTIVE")
     response["cluster"]["registeredContainerInstancesCount"].should.equal(0)
@@ -154,7 +154,7 @@ def test_register_task_definition():
     response["taskDefinition"]["family"].should.equal("test_ecs_task")
     response["taskDefinition"]["revision"].should.equal(1)
     response["taskDefinition"]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["taskDefinition"]["networkMode"].should.equal("bridge")
     response["taskDefinition"]["volumes"].should.equal([])
@@ -192,7 +192,7 @@ def test_register_task_definition():
 
     response["taskDefinition"]["revision"].should.equal(2)
     response["taskDefinition"]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:2".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:2"
     )
 
     # Registering with optional top-level params
@@ -293,10 +293,10 @@ def test_list_task_definitions():
     response = client.list_task_definitions()
     len(response["taskDefinitionArns"]).should.equal(2)
     response["taskDefinitionArns"][0].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["taskDefinitionArns"][1].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:2".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:2"
     )
 
 
@@ -356,10 +356,10 @@ def test_list_task_definitions_with_family_prefix():
     filtered_response = client.list_task_definitions(familyPrefix="test_ecs_task_a")
     len(filtered_response["taskDefinitionArns"]).should.equal(2)
     filtered_response["taskDefinitionArns"][0].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task_a:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task_a:1"
     )
     filtered_response["taskDefinitionArns"][1].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task_a:2".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task_a:2"
     )
 
 
@@ -419,12 +419,12 @@ def test_describe_task_definitions():
     )
     response = client.describe_task_definition(taskDefinition="test_ecs_task")
     response["taskDefinition"]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:3".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:3"
     )
 
     response = client.describe_task_definition(taskDefinition="test_ecs_task:2")
     response["taskDefinition"]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:2".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:2"
     )
     response["taskDefinition"]["taskRoleArn"].should.equal("my-task-role-arn")
     response["taskDefinition"]["executionRoleArn"].should.equal("my-execution-role-arn")
@@ -458,7 +458,7 @@ def test_deregister_task_definition_1():
     type(response["taskDefinition"]).should.be(dict)
     response["taskDefinition"]["status"].should.equal("INACTIVE")
     response["taskDefinition"]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["taskDefinition"]["containerDefinitions"][0]["name"].should.equal(
         "hello_world"
@@ -526,7 +526,7 @@ def test_create_service():
         desiredCount=2,
     )
     response["service"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["service"]["desiredCount"].should.equal(2)
     len(response["service"]["events"]).should.equal(0)
@@ -534,14 +534,12 @@ def test_create_service():
     response["service"]["pendingCount"].should.equal(0)
     response["service"]["runningCount"].should.equal(0)
     response["service"]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service"
-            ACCOUNT_ID
-        )
     )
     response["service"]["serviceName"].should.equal("test_ecs_service")
     response["service"]["status"].should.equal("ACTIVE")
     response["service"]["taskDefinition"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["service"]["schedulingStrategy"].should.equal("REPLICA")
     response["service"]["launchType"].should.equal("EC2")
@@ -618,7 +616,7 @@ def test_create_service_scheduling_strategy():
         schedulingStrategy="DAEMON",
     )
     response["service"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["service"]["desiredCount"].should.equal(2)
     len(response["service"]["events"]).should.equal(0)
@@ -626,14 +624,12 @@ def test_create_service_scheduling_strategy():
     response["service"]["pendingCount"].should.equal(0)
     response["service"]["runningCount"].should.equal(0)
     response["service"]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service"
-            ACCOUNT_ID
-        )
     )
     response["service"]["serviceName"].should.equal("test_ecs_service")
     response["service"]["status"].should.equal("ACTIVE")
     response["service"]["taskDefinition"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["service"]["schedulingStrategy"].should.equal("DAEMON")
 
@@ -684,16 +680,8 @@ def test_list_services():
         desiredCount=2,
     )
 
-    test_ecs_service1_arn = (
+    test_ecs_service1_arn = f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster1/test_ecs_service1"
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster1/test_ecs_service1".format(
+    test_ecs_service2_arn = f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster1/test_ecs_service2"
-            ACCOUNT_ID
-        )
-    )
-    test_ecs_service2_arn = (
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster1/test_ecs_service2".format(
-            ACCOUNT_ID
-        )
-    )
 
     cluster1_services = client.list_services(cluster="test_ecs_cluster1")
     len(cluster1_services["serviceArns"]).should.equal(2)
@@ -766,22 +754,16 @@ def test_describe_services():
         cluster="test_ecs_cluster",
         services=[
             "test_ecs_service1",
-            "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service2".format(
+            f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service2",
-                ACCOUNT_ID
-            ),
         ],
     )
     len(response["services"]).should.equal(2)
     response["services"][0]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service1".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service1"
-            ACCOUNT_ID
-        )
     )
     response["services"][0]["serviceName"].should.equal("test_ecs_service1")
     response["services"][1]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service2".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service2"
-            ACCOUNT_ID
-        )
     )
     response["services"][1]["serviceName"].should.equal("test_ecs_service2")
 
@@ -802,9 +784,7 @@ def test_describe_services():
         cluster="test_ecs_cluster",
         services=[
             "test_ecs_service1",
-            "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service2".format(
+            f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service2",
-                ACCOUNT_ID
-            ),
         ],
         include=["TAGS"],
     )
@@ -840,9 +820,7 @@ def test_describe_services_new_arn():
         cluster="test_ecs_cluster", services=["test_ecs_service1"]
     )
     response["services"][0]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service1".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service1"
-            ACCOUNT_ID
-        )
     )
 
 
@@ -889,23 +867,17 @@ def test_describe_services_scheduling_strategy():
         cluster="test_ecs_cluster",
         services=[
             "test_ecs_service1",
-            "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service2".format(
+            f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service2",
-                ACCOUNT_ID
-            ),
             "test_ecs_service3",
         ],
     )
     len(response["services"]).should.equal(3)
     response["services"][0]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service1".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service1"
-            ACCOUNT_ID
-        )
     )
     response["services"][0]["serviceName"].should.equal("test_ecs_service1")
     response["services"][1]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service2".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service2"
-            ACCOUNT_ID
-        )
     )
     response["services"][1]["serviceName"].should.equal("test_ecs_service2")
 
@@ -971,7 +943,7 @@ def test_describe_services_with_known_unknown_services():
             service_name,
             "unknown",
             service_arn,
-            "arn:aws:ecs:eu-central-1:{}:service/unknown-2".format(ACCOUNT_ID),
+            f"arn:aws:ecs:eu-central-1:{ACCOUNT_ID}:service/unknown-2",
         ],
     )
 
@@ -987,13 +959,11 @@ def test_describe_services_with_known_unknown_services():
     sorted(failures, key=lambda item: item["arn"]).should.equal(
         [
             {
-                "arn": "arn:aws:ecs:eu-central-1:{}:service/unknown".format(ACCOUNT_ID),
+                "arn": f"arn:aws:ecs:eu-central-1:{ACCOUNT_ID}:service/unknown",
                 "reason": "MISSING",
             },
             {
-                "arn": "arn:aws:ecs:eu-central-1:{}:service/unknown-2".format(
+                "arn": f"arn:aws:ecs:eu-central-1:{ACCOUNT_ID}:service/unknown-2",
-                    ACCOUNT_ID
-                ),
                 "reason": "MISSING",
             },
         ]
@@ -1093,7 +1063,7 @@ def test_delete_service():
         cluster="test_ecs_cluster", service="test_ecs_service"
     )
     response["service"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["service"]["desiredCount"].should.equal(0)
     len(response["service"]["events"]).should.equal(0)
@@ -1101,15 +1071,13 @@ def test_delete_service():
     response["service"]["pendingCount"].should.equal(0)
     response["service"]["runningCount"].should.equal(0)
     response["service"]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service"
-            ACCOUNT_ID
-        )
     )
     response["service"]["serviceName"].should.equal("test_ecs_service")
     response["service"]["status"].should.equal("ACTIVE")
     response["service"]["schedulingStrategy"].should.equal("REPLICA")
     response["service"]["taskDefinition"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
 
 
@@ -1146,7 +1114,7 @@ def test_delete_service__using_arns():
     )
     response = client.delete_service(cluster=cluster_arn, service=service_arn)
     response["service"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
 
 
@@ -1180,22 +1148,20 @@ def test_delete_service_force():
         cluster="test_ecs_cluster", service="test_ecs_service", force=True
     )
     response["service"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     len(response["service"]["events"]).should.equal(0)
     len(response["service"]["loadBalancers"]).should.equal(0)
     response["service"]["pendingCount"].should.equal(0)
     response["service"]["runningCount"].should.equal(0)
     response["service"]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service"
-            ACCOUNT_ID
-        )
     )
     response["service"]["serviceName"].should.equal("test_ecs_service")
     response["service"]["status"].should.equal("ACTIVE")
     response["service"]["schedulingStrategy"].should.equal("REPLICA")
     response["service"]["taskDefinition"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
 
 
@@ -1277,9 +1243,7 @@ def test_register_container_instance():
     response["containerInstance"]["ec2InstanceId"].should.equal(test_instance.id)
     full_arn = response["containerInstance"]["containerInstanceArn"]
     arn_part = full_arn.split("/")
-    arn_part[0].should.equal(
+    arn_part[0].should.equal(f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:container-instance")
-        "arn:aws:ecs:us-east-1:{}:container-instance".format(ACCOUNT_ID)
-    )
     arn_part[1].should.equal("test_ecs_cluster")
     arn_part[2].should.equal(str(UUID(arn_part[2])))
     response["containerInstance"]["status"].should.equal("ACTIVE")
@@ -1686,16 +1650,16 @@ def test_run_task():
     )
     len(response["tasks"]).should.equal(2)
     response["tasks"][0]["taskArn"].should.contain(
-        "arn:aws:ecs:us-east-1:{}:task/".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task/"
     )
     response["tasks"][0]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["tasks"][0]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["tasks"][0]["containerInstanceArn"].should.contain(
-        "arn:aws:ecs:us-east-1:{}:container-instance/".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:container-instance/"
     )
     response["tasks"][0]["overrides"].should.equal({})
     response["tasks"][0]["lastStatus"].should.equal("RUNNING")
@@ -1835,16 +1799,16 @@ def test_run_task_default_cluster():
     len(response["tasks"]).should.equal(2)
     response["tasks"][0].should.have.key("launchType").equals("FARGATE")
     response["tasks"][0]["taskArn"].should.match(
-        "arn:aws:ecs:us-east-1:{}:task/default/[a-z0-9-]+$".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task/default/[a-z0-9-]+$"
     )
     response["tasks"][0]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/default".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/default"
     )
     response["tasks"][0]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["tasks"][0]["containerInstanceArn"].should.contain(
-        "arn:aws:ecs:us-east-1:{}:container-instance/".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:container-instance/"
     )
     response["tasks"][0]["overrides"].should.equal({})
     response["tasks"][0]["lastStatus"].should.equal("RUNNING")
@@ -1975,18 +1939,16 @@ def test_start_task():
 
     len(response["tasks"]).should.equal(1)
     response["tasks"][0]["taskArn"].should.contain(
-        "arn:aws:ecs:us-east-1:{}:task/".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task/"
     )
     response["tasks"][0]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["tasks"][0]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["tasks"][0]["containerInstanceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{0}:container-instance/test_ecs_cluster/{1}".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:container-instance/test_ecs_cluster/{container_instance_id}"
-            ACCOUNT_ID, container_instance_id
-        )
     )
     response["tasks"][0]["overrides"].should.equal({})
     response["tasks"][0]["lastStatus"].should.equal("RUNNING")
@@ -2190,7 +2152,7 @@ def test_describe_task_definition_by_family():
         )
     )
     task["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     task["volumes"].should.equal([])
     task["status"].should.equal("ACTIVE")
@@ -2508,16 +2470,16 @@ def test_task_definitions_with_port_clash():
     )
     len(response["tasks"]).should.equal(1)
     response["tasks"][0]["taskArn"].should.contain(
-        "arn:aws:ecs:us-east-1:{}:task/".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task/"
     )
     response["tasks"][0]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["tasks"][0]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
     response["tasks"][0]["containerInstanceArn"].should.contain(
-        "arn:aws:ecs:us-east-1:{}:container-instance/".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:container-instance/"
     )
     response["tasks"][0]["overrides"].should.equal({})
     response["tasks"][0]["lastStatus"].should.equal("RUNNING")
@@ -2857,7 +2819,7 @@ def test_create_service_load_balancing():
         ],
     )
     response["service"]["clusterArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:cluster/test_ecs_cluster".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:cluster/test_ecs_cluster"
     )
     response["service"]["desiredCount"].should.equal(2)
     len(response["service"]["events"]).should.equal(0)
@@ -2875,14 +2837,12 @@ def test_create_service_load_balancing():
     response["service"]["pendingCount"].should.equal(0)
     response["service"]["runningCount"].should.equal(0)
     response["service"]["serviceArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:service/test_ecs_cluster/test_ecs_service".format(
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:service/test_ecs_cluster/test_ecs_service"
-            ACCOUNT_ID
-        )
     )
     response["service"]["serviceName"].should.equal("test_ecs_service")
     response["service"]["status"].should.equal("ACTIVE")
     response["service"]["taskDefinition"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
 
 
@@ -2912,7 +2872,7 @@ def test_list_tags_for_resource():
     type(response["taskDefinition"]).should.be(dict)
     response["taskDefinition"]["revision"].should.equal(1)
     response["taskDefinition"]["taskDefinitionArn"].should.equal(
-        "arn:aws:ecs:us-east-1:{}:task-definition/test_ecs_task:1".format(ACCOUNT_ID)
+        f"arn:aws:ecs:us-east-1:{ACCOUNT_ID}:task-definition/test_ecs_task:1"
     )
 
     task_definition_arn = response["taskDefinition"]["taskDefinitionArn"]
@@ -3255,7 +3215,7 @@ def test_create_task_set():
     )["services"][0]["serviceArn"]
     task_set["clusterArn"].should.equal(cluster_arn)
     task_set["serviceArn"].should.equal(service_arn)
-    task_set["taskDefinition"].should.match("{0}:1$".format(task_def_name))
+    task_set["taskDefinition"].should.match(f"{task_def_name}:1$")
     task_set["scale"].should.equal({"value": 100.0, "unit": "PERCENT"})
     task_set["loadBalancers"][0]["targetGroupArn"].should.equal(
         "arn:aws:elasticloadbalancing:us-east-1:01234567890:targetgroup/"
@@ -3384,12 +3344,12 @@ def test_describe_task_sets():
 
     task_sets[0].should.have.key("tags")
     task_sets.should.have.length_of(1)
-    task_sets[0]["taskDefinition"].should.match("{0}:1$".format(task_def_name))
+    task_sets[0]["taskDefinition"].should.match(f"{task_def_name}:1$")
     task_sets[0]["clusterArn"].should.equal(cluster_arn)
     task_sets[0]["serviceArn"].should.equal(service_arn)
-    task_sets[0]["serviceArn"].should.match("{0}$".format(service_name))
+    task_sets[0]["serviceArn"].should.match(f"{service_name}$")
     task_sets[0]["scale"].should.equal({"value": 100.0, "unit": "PERCENT"})
-    task_sets[0]["taskSetArn"].should.match("{0}$".format(task_sets[0]["id"]))
+    task_sets[0]["taskSetArn"].should.match(f"{task_sets[0]['id']}$")
     task_sets[0]["loadBalancers"][0]["targetGroupArn"].should.equal(
         "arn:aws:elasticloadbalancing:us-east-1:01234567890:targetgroup/"
         "c26b93c1bc35466ba792d5b08fe6a5bc/ec39113f8831453a"

tests/test_efs/test_file_system.py

@@ -262,7 +262,7 @@ def test_describe_file_systems_aws_create_sample_2(efs):
 def test_describe_file_systems_paging(efs):
     # Create several file systems.
     for i in range(10):
-        efs.create_file_system(CreationToken="foobar_{}".format(i))
+        efs.create_file_system(CreationToken=f"foobar_{i}")
 
     # First call (Start)
     # ------------------

tests/test_efs/test_mount_target.py

@@ -91,9 +91,9 @@ def test_create_mount_target_aws_sample_2(efs, ec2, file_system, subnet):
         ip_addr = ip_addr_obj.exploded
         break
     else:
-        assert False, "Could not generate an IP address from CIDR block: {}".format(
+        assert (
-            subnet["CidrBlock"]
+            False
-        )
+        ), f"Could not generate an IP address from CIDR block: {subnet['CidrBlock']}"
     desc_sg_resp = ec2.describe_security_groups()
     security_group = desc_sg_resp["SecurityGroups"][0]
     security_group_id = security_group["GroupId"]
@@ -216,8 +216,8 @@ def test_create_mount_target_too_many_security_groups(efs, ec2, file_system, sub
     for i in range(6):
         sg_info = ec2.create_security_group(
             VpcId=subnet["VpcId"],
-            GroupName="sg-{}".format(i),
+            GroupName=f"sg-{i}",
-            Description="SG-{} protects us from the Goa'uld.".format(i),
+            Description=f"SG-{i} protects us from the Goa'uld.",
         )
         sg_id_list.append(sg_info["GroupId"])
     with pytest.raises(ClientError) as exc_info:

tests/test_efs/test_server.py

@@ -61,7 +61,7 @@ def test_efs_file_system_describe(efs_client):
 
 
 def test_efs_file_system_delete(file_system_id, efs_client):
-    res = efs_client.delete("/2015-02-01/file-systems/{}".format(file_system_id))
+    res = efs_client.delete(f"/2015-02-01/file-systems/{file_system_id}")
     assert res.status_code == 204
 
 
@@ -84,12 +84,10 @@ def test_efs_mount_target_delete(file_system_id, subnet_id, efs_client):
         json={"FileSystemId": file_system_id, "SubnetId": subnet_id},
     )
     mt_id = create_res.json["MountTargetId"]
-    res = efs_client.delete("/2015-02-01/mount-targets/{}".format(mt_id))
+    res = efs_client.delete(f"/2015-02-01/mount-targets/{mt_id}")
     assert res.status_code == 204
 
 
 def test_efs_describe_backup_policy(file_system_id, efs_client):
-    res = efs_client.get(
+    res = efs_client.get(f"/2015-02-01/file-systems/{file_system_id}/backup-policy")
-        "/2015-02-01/file-systems/{}/backup-policy".format(file_system_id)
-    )
     assert res.status_code == 200

tests/test_eks/test_eks_utils.py

@@ -60,7 +60,7 @@ def generate_fargate_profiles(client, cluster_name, num_profiles, minimal):
         client.create_fargate_profile(
             fargateProfileName=generate_random_name(),
             clusterName=cluster_name,
-            **_input_builder(FargateProfileInputs, minimal)
+            **_input_builder(FargateProfileInputs, minimal),
         )[ResponseAttributes.FARGATE_PROFILE][
             FargateProfileAttributes.FARGATE_PROFILE_NAME
         ]
@@ -78,17 +78,14 @@ def generate_nodegroups(client, cluster_name, num_nodegroups, minimal):
         client.create_nodegroup(
             nodegroupName=generate_random_name(),
             clusterName=cluster_name,
-            **_input_builder(NodegroupInputs, minimal)
+            **_input_builder(NodegroupInputs, minimal),
         )[ResponseAttributes.NODEGROUP][NodegroupAttributes.NODEGROUP_NAME]
         for _ in range(num_nodegroups)
     ]
 
 
 def generate_dict(prefix, count):
-    return {
+    return {f"{prefix}_{_count}": str(_count) for _count in range(count)}
-        "{prefix}_{count}".format(prefix=prefix, count=_count): str(_count)
-        for _count in range(count)
-    }
 
 
 def is_valid_uri(value):

tests/test_elastictranscoder/test_elastictranscoder.py

@@ -24,9 +24,7 @@ def test_create_simple_pipeline():
     pipeline.should.have.key("Id")
     pipeline.should.have.key("Name").being.equal("testpipeline")
     pipeline.should.have.key("Arn").being.equal(
-        "arn:aws:elastictranscoder:{}:{}:pipeline/{}".format(
+        f"arn:aws:elastictranscoder:{region}:{ACCOUNT_ID}:pipeline/{pipeline['Id']}"
-            region, ACCOUNT_ID, pipeline["Id"]
-        )
     )
     pipeline.should.have.key("Status").being.equal("Active")
     pipeline.should.have.key("InputBucket").being.equal("inputtest")
@@ -64,9 +62,7 @@ def test_create_pipeline_with_content_config():
     pipeline.should.have.key("Id")
     pipeline.should.have.key("Name").being.equal("testpipeline")
     pipeline.should.have.key("Arn").being.equal(
-        "arn:aws:elastictranscoder:{}:{}:pipeline/{}".format(
+        f"arn:aws:elastictranscoder:{region}:{ACCOUNT_ID}:pipeline/{pipeline['Id']}"
-            region, ACCOUNT_ID, pipeline["Id"]
-        )
     )
     pipeline.should.have.key("Status").being.equal("Active")
     pipeline.should.have.key("InputBucket").being.equal("inputtest")
@@ -186,9 +182,7 @@ def test_list_pipelines():
     pipeline.should.have.key("Id")
     pipeline.should.have.key("Name").being.equal("testpipeline")
     pipeline.should.have.key("Arn").being.equal(
-        "arn:aws:elastictranscoder:{}:{}:pipeline/{}".format(
+        f"arn:aws:elastictranscoder:{region}:{ACCOUNT_ID}:pipeline/{pipeline['Id']}"
-            region, ACCOUNT_ID, pipeline["Id"]
-        )
     )
     pipeline.should.have.key("Status").being.equal("Active")
     pipeline.should.have.key("InputBucket").being.equal("inputtest")
@@ -227,9 +221,7 @@ def test_read_pipeline():
     pipeline.should.have.key("Id")
     pipeline.should.have.key("Name").being.equal("testpipeline")
     pipeline.should.have.key("Arn").being.equal(
-        "arn:aws:elastictranscoder:{}:{}:pipeline/{}".format(
+        f"arn:aws:elastictranscoder:{region}:{ACCOUNT_ID}:pipeline/{pipeline['Id']}"
-            region, ACCOUNT_ID, pipeline["Id"]
-        )
     )
     pipeline.should.have.key("Status").being.equal("Active")
     pipeline.should.have.key("InputBucket").being.equal("inputtest")
@@ -271,9 +263,7 @@ def test_read_nonexisting_pipeline_format():
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceNotFoundException")
     err["Message"].should.equal(
-        "The specified pipeline was not found: account={}, pipelineId={}.".format(
+        f"The specified pipeline was not found: account={ACCOUNT_ID}, pipelineId={pipeline_id}."
-            ACCOUNT_ID, pipeline_id
-        )
     )
 
 
@@ -298,9 +288,7 @@ def test_update_pipeline_name():
     pipeline.should.have.key("Id")
     pipeline.should.have.key("Name").being.equal("newtestpipeline")
     pipeline.should.have.key("Arn").being.equal(
-        "arn:aws:elastictranscoder:{}:{}:pipeline/{}".format(
+        f"arn:aws:elastictranscoder:{region}:{ACCOUNT_ID}:pipeline/{pipeline['Id']}"
-            region, ACCOUNT_ID, pipeline["Id"]
-        )
     )
     pipeline.should.have.key("Status").being.equal("Active")
     pipeline.should.have.key("InputBucket").being.equal("inputtest")
@@ -369,9 +357,7 @@ def test_update_nonexisting_pipeline():
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceNotFoundException")
     err["Message"].should.equal(
-        "The specified pipeline was not found: account={}, pipelineId={}.".format(
+        f"The specified pipeline was not found: account={ACCOUNT_ID}, pipelineId={pipeline_id}."
-            ACCOUNT_ID, pipeline_id
-        )
     )
 
 
@@ -395,4 +381,4 @@ def test_delete_pipeline():
 
 
 def create_role_name(name):
-    return "arn:aws:iam::{}:role/{}".format(ACCOUNT_ID, name)
+    return f"arn:aws:iam::{ACCOUNT_ID}:role/{name}"

tests/test_elb/test_elb.py

@@ -248,7 +248,7 @@ def test_describe_paginated_balancers():
 
     for i in range(51):
         client.create_load_balancer(
-            LoadBalancerName="my-lb%d" % i,
+            LoadBalancerName=f"my-lb{i}",
             Listeners=[
                 {"Protocol": "tcp", "LoadBalancerPort": 80, "InstancePort": 8080}
             ],

tests/test_elbv2/test_elbv2.py

@@ -399,7 +399,7 @@ def test_describe_paginated_balancers():
 
     for i in range(51):
         conn.create_load_balancer(
-            Name="my-lb%d" % i,
+            Name=f"my-lb{i}",
             Subnets=[subnet1.id, subnet2.id],
             SecurityGroups=[security_group.id],
             Scheme="internal",
@@ -1685,9 +1685,7 @@ def test_cognito_action_listener_rule():
     action = {
         "Type": "authenticate-cognito",
         "AuthenticateCognitoConfig": {
-            "UserPoolArn": "arn:aws:cognito-idp:us-east-1:{}:userpool/us-east-1_ABCD1234".format(
+            "UserPoolArn": f"arn:aws:cognito-idp:us-east-1:{ACCOUNT_ID}:userpool/us-east-1_ABCD1234",
-                ACCOUNT_ID
-            ),
             "UserPoolClientId": "abcd1234abcd",
             "UserPoolDomain": "testpool",
             "AuthenticationRequestExtraParams": {"param": "test"},

tests/test_elbv2/test_elbv2_cloudformation.py

@@ -144,9 +144,7 @@ def test_cognito_action_listener_rule_cloudformation():
                         {
                             "Type": "authenticate-cognito",
                             "AuthenticateCognitoConfig": {
-                                "UserPoolArn": "arn:aws:cognito-idp:us-east-1:{}:userpool/us-east-1_ABCD1234".format(
+                                "UserPoolArn": f"arn:aws:cognito-idp:us-east-1:{ACCOUNT_ID}:userpool/us-east-1_ABCD1234",
-                                    ACCOUNT_ID
-                                ),
                                 "UserPoolClientId": "abcd1234abcd",
                                 "UserPoolDomain": "testpool",
                             },
@@ -175,9 +173,7 @@ def test_cognito_action_listener_rule_cloudformation():
             {
                 "Type": "authenticate-cognito",
                 "AuthenticateCognitoConfig": {
-                    "UserPoolArn": "arn:aws:cognito-idp:us-east-1:{}:userpool/us-east-1_ABCD1234".format(
+                    "UserPoolArn": f"arn:aws:cognito-idp:us-east-1:{ACCOUNT_ID}:userpool/us-east-1_ABCD1234",
-                        ACCOUNT_ID
-                    ),
                     "UserPoolClientId": "abcd1234abcd",
                     "UserPoolDomain": "testpool",
                 },

tests/test_elbv2/test_elbv2_target_groups.py

@@ -131,11 +131,7 @@ def test_create_target_group_and_listeners():
         Protocol="HTTPS",
         Port=443,
         Certificates=[
-            {
+            {"CertificateArn": f"arn:aws:iam:{ACCOUNT_ID}:server-certificate/test-cert"}
-                "CertificateArn": "arn:aws:iam:{}:server-certificate/test-cert".format(
-                    ACCOUNT_ID
-                )
-            }
         ],
         DefaultActions=[actions],
     )
@@ -143,13 +139,7 @@ def test_create_target_group_and_listeners():
     listener.get("Port").should.equal(443)
     listener.get("Protocol").should.equal("HTTPS")
     listener.get("Certificates").should.equal(
-        [
+        [{"CertificateArn": f"arn:aws:iam:{ACCOUNT_ID}:server-certificate/test-cert"}]
-            {
-                "CertificateArn": "arn:aws:iam:{}:server-certificate/test-cert".format(
-                    ACCOUNT_ID
-                )
-            }
-        ]
     )
     listener.get("DefaultActions").should.equal(
         [{"TargetGroupArn": target_group_arn, "Type": "forward"}]

tests/test_emr/test_emr_boto3.py

@@ -183,9 +183,7 @@ def test_describe_cluster():
     cl["TerminationProtected"].should.equal(False)
     cl["VisibleToAllUsers"].should.equal(True)
     cl["ClusterArn"].should.equal(
-        "arn:aws:elasticmapreduce:{0}:{1}:cluster/{2}".format(
+        f"arn:aws:elasticmapreduce:{region_name}:{ACCOUNT_ID}:cluster/{cluster_id}"
-            region_name, ACCOUNT_ID, cluster_id
-        )
     )
 
 
@@ -396,7 +394,7 @@ def test_run_job_flow():
     args = deepcopy(run_job_flow_args)
     resp = client.run_job_flow(**args)
     resp["ClusterArn"].startswith(
-        "arn:aws:elasticmapreduce:{0}:{1}:cluster/".format(region_name, ACCOUNT_ID)
+        f"arn:aws:elasticmapreduce:{region_name}:{ACCOUNT_ID}:cluster/"
     )
     job_flow_id = resp["JobFlowId"]
     resp = client.describe_job_flows(JobFlowIds=[job_flow_id])["JobFlows"][0]
@@ -584,9 +582,7 @@ def test_put_remove_auto_scaling_policy():
     del resp["AutoScalingPolicy"]["Status"]
     resp["AutoScalingPolicy"].should.equal(auto_scaling_policy_with_cluster_id)
     resp["ClusterArn"].should.equal(
-        "arn:aws:elasticmapreduce:{0}:{1}:cluster/{2}".format(
+        f"arn:aws:elasticmapreduce:{region_name}:{ACCOUNT_ID}:cluster/{cluster_id}"
-            region_name, ACCOUNT_ID, cluster_id
-        )
     )
 
     core_instance_group = [

tests/test_events/test_events.py

@@ -185,7 +185,7 @@ def test_describe_rule():
 
     response["Name"].should.equal(rule_name)
     response["Arn"].should.equal(
-        "arn:aws:events:us-west-2:{0}:rule/{1}".format(ACCOUNT_ID, rule_name)
+        f"arn:aws:events:us-west-2:{ACCOUNT_ID}:rule/{rule_name}"
     )
 
 
@@ -201,7 +201,7 @@ def test_describe_rule_with_event_bus_name():
         EventPattern=json.dumps({"account": [ACCOUNT_ID]}),
         State="DISABLED",
         Description="test rule",
-        RoleArn="arn:aws:iam::{}:role/test-role".format(ACCOUNT_ID),
+        RoleArn=f"arn:aws:iam::{ACCOUNT_ID}:role/test-role",
         EventBusName=event_bus_name,
     )
 
@@ -210,18 +210,14 @@ def test_describe_rule_with_event_bus_name():
 
     # then
     response["Arn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:rule/{1}/{2}".format(
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:rule/{event_bus_name}/{rule_name}"
-            ACCOUNT_ID, event_bus_name, rule_name
-        )
     )
     response["CreatedBy"].should.equal(ACCOUNT_ID)
     response["Description"].should.equal("test rule")
     response["EventBusName"].should.equal(event_bus_name)
     json.loads(response["EventPattern"]).should.equal({"account": [ACCOUNT_ID]})
     response["Name"].should.equal(rule_name)
-    response["RoleArn"].should.equal(
+    response["RoleArn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:role/test-role")
-        "arn:aws:iam::{}:role/test-role".format(ACCOUNT_ID)
-    )
     response["State"].should.equal("DISABLED")
 
     response.should_not.have.key("ManagedBy")
@@ -505,9 +501,7 @@ def test_put_targets_error_missing_parameter_sqs_fifo():
             Targets=[
                 {
                     "Id": "sqs-fifo",
-                    "Arn": "arn:aws:sqs:eu-central-1:{}:test-queue.fifo".format(
+                    "Arn": f"arn:aws:sqs:eu-central-1:{ACCOUNT_ID}:test-queue.fifo",
-                        ACCOUNT_ID
-                    ),
                 }
             ],
         )
@@ -770,7 +764,7 @@ def test_create_event_bus():
     response = client.create_event_bus(Name="test-bus")
 
     response["EventBusArn"].should.equal(
-        "arn:aws:events:us-east-1:{}:event-bus/test-bus".format(ACCOUNT_ID)
+        f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/test-bus"
     )
 
 
@@ -808,7 +802,7 @@ def test_describe_event_bus():
 
     response["Name"].should.equal("default")
     response["Arn"].should.equal(
-        "arn:aws:events:us-east-1:{}:event-bus/default".format(ACCOUNT_ID)
+        f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/default"
     )
     response.should_not.have.key("Policy")
 
@@ -824,7 +818,7 @@ def test_describe_event_bus():
 
     response["Name"].should.equal("test-bus")
     response["Arn"].should.equal(
-        "arn:aws:events:us-east-1:{}:event-bus/test-bus".format(ACCOUNT_ID)
+        f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/test-bus"
     )
     json.loads(response["Policy"]).should.equal(
         {
@@ -835,9 +829,7 @@ def test_describe_event_bus():
                     "Effect": "Allow",
                     "Principal": {"AWS": "arn:aws:iam::111111111111:root"},
                     "Action": "events:PutEvents",
-                    "Resource": "arn:aws:events:us-east-1:{}:event-bus/test-bus".format(
+                    "Resource": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/test-bus",
-                        ACCOUNT_ID
-                    ),
                 }
             ],
         }
@@ -868,33 +860,23 @@ def test_list_event_buses():
         [
             {
                 "Name": "default",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/default".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/default",
-                    ACCOUNT_ID
-                ),
             },
             {
                 "Name": "other-bus-1",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/other-bus-1".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/other-bus-1",
-                    ACCOUNT_ID
-                ),
             },
             {
                 "Name": "other-bus-2",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/other-bus-2".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/other-bus-2",
-                    ACCOUNT_ID
-                ),
             },
             {
                 "Name": "test-bus-1",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/test-bus-1".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/test-bus-1",
-                    ACCOUNT_ID
-                ),
             },
             {
                 "Name": "test-bus-2",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/test-bus-2".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/test-bus-2",
-                    ACCOUNT_ID
-                ),
             },
         ]
     )
@@ -906,15 +888,11 @@ def test_list_event_buses():
         [
             {
                 "Name": "other-bus-1",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/other-bus-1".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/other-bus-1",
-                    ACCOUNT_ID
-                ),
             },
             {
                 "Name": "other-bus-2",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/other-bus-2".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/other-bus-2",
-                    ACCOUNT_ID
-                ),
             },
         ]
     )
@@ -936,9 +914,7 @@ def test_delete_event_bus():
         [
             {
                 "Name": "default",
-                "Arn": "arn:aws:events:us-east-1:{}:event-bus/default".format(
+                "Arn": f"arn:aws:events:us-east-1:{ACCOUNT_ID}:event-bus/default",
-                    ACCOUNT_ID
-                ),
             }
         ]
     )
@@ -1016,9 +992,7 @@ def test_tag_resource_error_unknown_arn():
     # when
     with pytest.raises(ClientError) as e:
         client.tag_resource(
-            ResourceARN="arn:aws:events:eu-central-1:{0}:rule/unknown".format(
+            ResourceARN=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:rule/unknown",
-                ACCOUNT_ID
-            ),
             Tags=[],
         )
 
@@ -1040,9 +1014,7 @@ def test_untag_resource_error_unknown_arn():
     # when
     with pytest.raises(ClientError) as e:
         client.untag_resource(
-            ResourceARN="arn:aws:events:eu-central-1:{0}:rule/unknown".format(
+            ResourceARN=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:rule/unknown",
-                ACCOUNT_ID
-            ),
             TagKeys=[],
         )
 
@@ -1064,9 +1036,7 @@ def test_list_tags_for_resource_error_unknown_arn():
     # when
     with pytest.raises(ClientError) as e:
         client.list_tags_for_resource(
-            ResourceARN="arn:aws:events:eu-central-1:{0}:rule/unknown".format(
+            ResourceARN=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:rule/unknown"
-                ACCOUNT_ID
-            )
         )
 
     # then
@@ -1088,24 +1058,22 @@ def test_create_archive():
     # when
     response = client.create_archive(
         ArchiveName=archive_name,
-        EventSourceArn="arn:aws:events:eu-central-1:{}:event-bus/default".format(
+        EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default",
-            ACCOUNT_ID
-        ),
     )
 
     # then
     response["ArchiveArn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:archive/{1}".format(ACCOUNT_ID, archive_name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/{archive_name}"
     )
     response["CreationTime"].should.be.a(datetime)
     response["State"].should.equal("ENABLED")
 
     # check for archive rule existence
-    rule_name = "Events-Archive-{}".format(archive_name)
+    rule_name = f"Events-Archive-{archive_name}"
     response = client.describe_rule(Name=rule_name)
 
     response["Arn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:rule/{1}".format(ACCOUNT_ID, rule_name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:rule/{rule_name}"
     )
     response["CreatedBy"].should.equal(ACCOUNT_ID)
     response["EventBusName"].should.equal("default")
@@ -1142,7 +1110,7 @@ def test_create_archive_custom_event_bus():
 
     # then
     response["ArchiveArn"].should.equal(
-        "arn:aws:events:eu-central-1:{}:archive/test-archive".format(ACCOUNT_ID)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/test-archive"
     )
     response["CreationTime"].should.be.a(datetime)
     response["State"].should.equal("ENABLED")
@@ -1159,7 +1127,7 @@ def test_create_archive_error_long_name():
         client.create_archive(
             ArchiveName=name,
             EventSourceArn=(
-                "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+                f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
             ),
         )
 
@@ -1170,8 +1138,8 @@ def test_create_archive_error_long_name():
     ex.response["Error"]["Code"].should.contain("ValidationException")
     ex.response["Error"]["Message"].should.equal(
         " 1 validation error detected: "
-        "Value '{}' at 'archiveName' failed to satisfy constraint: "
+        f"Value '{name}' at 'archiveName' failed to satisfy constraint: "
-        "Member must have length less than or equal to 48".format(name)
+        "Member must have length less than or equal to 48"
     )
 
 
@@ -1185,7 +1153,7 @@ def test_create_archive_error_invalid_event_pattern():
         client.create_archive(
             ArchiveName="test-archive",
             EventSourceArn=(
-                "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+                f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
             ),
             EventPattern="invalid",
         )
@@ -1210,7 +1178,7 @@ def test_create_archive_error_invalid_event_pattern_not_an_array():
         client.create_archive(
             ArchiveName="test-archive",
             EventSourceArn=(
-                "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+                f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
             ),
             EventPattern=json.dumps(
                 {
@@ -1243,9 +1211,7 @@ def test_create_archive_error_unknown_event_bus():
         client.create_archive(
             ArchiveName="test-archive",
             EventSourceArn=(
-                "arn:aws:events:eu-central-1:{}:event-bus/{}".format(
+                f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/{event_bus_name}"
-                    ACCOUNT_ID, event_bus_name
-                )
             ),
         )
 
@@ -1255,7 +1221,7 @@ def test_create_archive_error_unknown_event_bus():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
     ex.response["Error"]["Message"].should.equal(
-        "Event bus {} does not exist.".format(event_bus_name)
+        f"Event bus {event_bus_name} does not exist."
     )
 
 
@@ -1264,7 +1230,7 @@ def test_create_archive_error_duplicate():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-archive"
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     client.create_archive(ArchiveName=name, EventSourceArn=source_arn)
 
     # when
@@ -1284,7 +1250,7 @@ def test_describe_archive():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-archive"
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     event_pattern = json.dumps({"key": ["value"]})
     client.create_archive(
         ArchiveName=name,
@@ -1298,7 +1264,7 @@ def test_describe_archive():
 
     # then
     response["ArchiveArn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:archive/{1}".format(ACCOUNT_ID, name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/{name}"
     )
     response["ArchiveName"].should.equal(name)
     response["CreationTime"].should.be.a(datetime)
@@ -1326,9 +1292,7 @@ def test_describe_archive_error_unknown_archive():
     ex.operation_name.should.equal("DescribeArchive")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"Archive {name} does not exist.")
-        "Archive {} does not exist.".format(name)
-    )
 
 
 @mock_events
@@ -1336,7 +1300,7 @@ def test_list_archives():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-archive"
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     event_pattern = json.dumps({"key": ["value"]})
     client.create_archive(
         ArchiveName=name,
@@ -1368,7 +1332,7 @@ def test_list_archives():
 def test_list_archives_with_name_prefix():
     # given
     client = boto3.client("events", "eu-central-1")
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     client.create_archive(ArchiveName="test", EventSourceArn=source_arn)
     client.create_archive(ArchiveName="test-archive", EventSourceArn=source_arn)
 
@@ -1384,7 +1348,7 @@ def test_list_archives_with_name_prefix():
 def test_list_archives_with_source_arn():
     # given
     client = boto3.client("events", "eu-central-1")
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     source_arn_2 = client.create_event_bus(Name="test-bus")["EventBusArn"]
     client.create_archive(ArchiveName="test", EventSourceArn=source_arn)
     client.create_archive(ArchiveName="test-archive", EventSourceArn=source_arn_2)
@@ -1401,7 +1365,7 @@ def test_list_archives_with_source_arn():
 def test_list_archives_with_state():
     # given
     client = boto3.client("events", "eu-central-1")
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     client.create_archive(ArchiveName="test", EventSourceArn=source_arn)
     client.create_archive(ArchiveName="test-archive", EventSourceArn=source_arn)
 
@@ -1459,7 +1423,7 @@ def test_update_archive():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-archive"
-    source_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(ACCOUNT_ID)
+    source_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
     event_pattern = json.dumps({"key": ["value"]})
     archive_arn = client.create_archive(ArchiveName=name, EventSourceArn=source_arn)[
         "ArchiveArn"
@@ -1499,9 +1463,7 @@ def test_update_archive_error_invalid_event_pattern():
     name = "test-archive"
     client.create_archive(
         ArchiveName=name,
-        EventSourceArn="arn:aws:events:eu-central-1:{}:event-bus/default".format(
+        EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default",
-            ACCOUNT_ID
-        ),
     )
 
     # when
@@ -1533,9 +1495,7 @@ def test_update_archive_error_unknown_archive():
     ex.operation_name.should.equal("UpdateArchive")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"Archive {name} does not exist.")
-        "Archive {} does not exist.".format(name)
-    )
 
 
 @mock_events
@@ -1545,9 +1505,7 @@ def test_delete_archive():
     name = "test-archive"
     client.create_archive(
         ArchiveName=name,
-        EventSourceArn="arn:aws:events:eu-central-1:{}:event-bus/default".format(
+        EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default",
-            ACCOUNT_ID
-        ),
     )
 
     # when
@@ -1573,9 +1531,7 @@ def test_delete_archive_error_unknown_archive():
     ex.operation_name.should.equal("DeleteArchive")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"Archive {name} does not exist.")
-        "Archive {} does not exist.".format(name)
-    )
 
 
 @mock_events
@@ -1585,9 +1541,7 @@ def test_archive_actual_events():
     name = "test-archive"
     name_2 = "test-archive-no-match"
     name_3 = "test-archive-matches"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     event = {
         "Source": "source",
         "DetailType": "type",
@@ -1629,9 +1583,7 @@ def test_archive_actual_events():
 def test_archive_event_with_bus_arn():
     # given
     client = boto3.client("events", "eu-central-1")
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_name = "mock_archive"
     event_with_bus_arn = {
         "Source": "source",
@@ -1658,9 +1610,7 @@ def test_start_replay():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-replay"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-archive", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -1676,7 +1626,7 @@ def test_start_replay():
 
     # then
     response["ReplayArn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:replay/{1}".format(ACCOUNT_ID, name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:replay/{name}"
     )
     response["ReplayStartTime"].should.be.a(datetime)
     response["State"].should.equal("STARTING")
@@ -1692,15 +1642,11 @@ def test_start_replay_error_unknown_event_bus():
     with pytest.raises(ClientError) as e:
         client.start_replay(
             ReplayName="test",
-            EventSourceArn="arn:aws:events:eu-central-1:{}:archive/test".format(
+            EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/test",
-                ACCOUNT_ID
-            ),
             EventStartTime=datetime(2021, 2, 1),
             EventEndTime=datetime(2021, 2, 2),
             Destination={
-                "Arn": "arn:aws:events:eu-central-1:{0}:event-bus/{1}".format(
+                "Arn": f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/{event_bus_name}",
-                    ACCOUNT_ID, event_bus_name
-                ),
             },
         )
 
@@ -1710,7 +1656,7 @@ def test_start_replay_error_unknown_event_bus():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
     ex.response["Error"]["Message"].should.equal(
-        "Event bus {} does not exist.".format(event_bus_name)
+        f"Event bus {event_bus_name} does not exist."
     )
 
 
@@ -1723,9 +1669,7 @@ def test_start_replay_error_invalid_event_bus_arn():
     with pytest.raises(ClientError) as e:
         client.start_replay(
             ReplayName="test",
-            EventSourceArn="arn:aws:events:eu-central-1:{}:archive/test".format(
+            EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/test",
-                ACCOUNT_ID
-            ),
             EventStartTime=datetime(2021, 2, 1),
             EventEndTime=datetime(2021, 2, 2),
             Destination={
@@ -1753,15 +1697,11 @@ def test_start_replay_error_unknown_archive():
     with pytest.raises(ClientError) as e:
         client.start_replay(
             ReplayName="test",
-            EventSourceArn="arn:aws:events:eu-central-1:{0}:archive/{1}".format(
+            EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/{archive_name}",
-                ACCOUNT_ID, archive_name
-            ),
             EventStartTime=datetime(2021, 2, 1),
             EventEndTime=datetime(2021, 2, 2),
             Destination={
-                "Arn": "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+                "Arn": f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default",
-                    ACCOUNT_ID
-                ),
             },
         )
 
@@ -1772,7 +1712,7 @@ def test_start_replay_error_unknown_archive():
     ex.response["Error"]["Code"].should.contain("ValidationException")
     ex.response["Error"]["Message"].should.equal(
         "Parameter EventSourceArn is not valid. "
-        "Reason: Archive {} does not exist.".format(archive_name)
+        f"Reason: Archive {archive_name} does not exist."
     )
 
 
@@ -1782,9 +1722,7 @@ def test_start_replay_error_cross_event_bus():
     client = boto3.client("events", "eu-central-1")
     archive_arn = client.create_archive(
         ArchiveName="test-archive",
-        EventSourceArn="arn:aws:events:eu-central-1:{}:event-bus/default".format(
+        EventSourceArn=f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default",
-            ACCOUNT_ID
-        ),
     )["ArchiveArn"]
     event_bus_arn = client.create_event_bus(Name="test-bus")["EventBusArn"]
 
@@ -1813,9 +1751,7 @@ def test_start_replay_error_cross_event_bus():
 def test_start_replay_error_invalid_end_time():
     # given
     client = boto3.client("events", "eu-central-1")
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-archive", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -1846,9 +1782,7 @@ def test_start_replay_error_duplicate():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-replay"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-archive", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -1875,9 +1809,7 @@ def test_start_replay_error_duplicate():
     ex.operation_name.should.equal("StartReplay")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceAlreadyExistsException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"Replay {name} already exists.")
-        "Replay {} already exists.".format(name)
-    )
 
 
 @mock_events
@@ -1885,9 +1817,7 @@ def test_describe_replay():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-replay"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-archive", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -1910,7 +1840,7 @@ def test_describe_replay():
     response["EventStartTime"].should.equal(datetime(2021, 2, 1, tzinfo=pytz.utc))
     response["EventEndTime"].should.equal(datetime(2021, 2, 2, tzinfo=pytz.utc))
     response["ReplayArn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:replay/{1}".format(ACCOUNT_ID, name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:replay/{name}"
     )
     response["ReplayName"].should.equal(name)
     response["ReplayStartTime"].should.be.a(datetime)
@@ -1933,9 +1863,7 @@ def test_describe_replay_error_unknown_replay():
     ex.operation_name.should.equal("DescribeReplay")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"Replay {name} does not exist.")
-        "Replay {} does not exist.".format(name)
-    )
 
 
 @mock_events
@@ -1943,9 +1871,7 @@ def test_list_replays():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-replay"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-replay", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -1977,9 +1903,7 @@ def test_list_replays():
 def test_list_replays_with_name_prefix():
     # given
     client = boto3.client("events", "eu-central-1")
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-replay", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -2010,9 +1934,7 @@ def test_list_replays_with_name_prefix():
 def test_list_replays_with_source_arn():
     # given
     client = boto3.client("events", "eu-central-1")
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-replay", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -2042,9 +1964,7 @@ def test_list_replays_with_source_arn():
 def test_list_replays_with_state():
     # given
     client = boto3.client("events", "eu-central-1")
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-replay", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -2117,9 +2037,7 @@ def test_cancel_replay():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-replay"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-archive", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -2137,7 +2055,7 @@ def test_cancel_replay():
 
     # then
     response["ReplayArn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:replay/{1}".format(ACCOUNT_ID, name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:replay/{name}"
     )
     response["State"].should.equal("CANCELLING")
 
@@ -2160,9 +2078,7 @@ def test_cancel_replay_error_unknown_replay():
     ex.operation_name.should.equal("CancelReplay")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("ResourceNotFoundException")
-    ex.response["Error"]["Message"].should.equal(
+    ex.response["Error"]["Message"].should.equal(f"Replay {name} does not exist.")
-        "Replay {} does not exist.".format(name)
-    )
 
 
 @mock_events
@@ -2170,9 +2086,7 @@ def test_cancel_replay_error_illegal_state():
     # given
     client = boto3.client("events", "eu-central-1")
     name = "test-replay"
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     archive_arn = client.create_archive(
         ArchiveName="test-archive", EventSourceArn=event_bus_arn
     )["ArchiveArn"]
@@ -2196,7 +2110,7 @@ def test_cancel_replay_error_illegal_state():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("IllegalStatusException")
     ex.response["Error"]["Message"].should.equal(
-        "Replay {} is not in a valid state for this operation.".format(name)
+        f"Replay {name} is not in a valid state for this operation."
     )
 
 
@@ -2209,18 +2123,14 @@ def test_start_replay_send_to_log_group():
     log_group_name = "/test-group"
     rule_name = "test-rule"
     logs_client.create_log_group(logGroupName=log_group_name)
-    event_bus_arn = "arn:aws:events:eu-central-1:{}:event-bus/default".format(
+    event_bus_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:event-bus/default"
-        ACCOUNT_ID
-    )
     client.put_rule(Name=rule_name, EventPattern=json.dumps({"account": [ACCOUNT_ID]}))
     client.put_targets(
         Rule=rule_name,
         Targets=[
             {
                 "Id": "test",
-                "Arn": "arn:aws:logs:eu-central-1:{0}:log-group:{1}".format(
+                "Arn": f"arn:aws:logs:eu-central-1:{ACCOUNT_ID}:log-group:{log_group_name}",
-                    ACCOUNT_ID, log_group_name
-                ),
             }
         ],
     )
@@ -2296,13 +2206,13 @@ def test_create_and_list_connections():
     )
 
     response.get("ConnectionArn").should.contain(
-        "arn:aws:events:eu-central-1:{0}:connection/test/".format(ACCOUNT_ID)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:connection/test/"
     )
 
     response = client.list_connections()
 
     response.get("Connections")[0].get("ConnectionArn").should.contain(
-        "arn:aws:events:eu-central-1:{0}:connection/test/".format(ACCOUNT_ID)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:connection/test/"
     )
 
 

tests/test_events/test_events_cloudformation.py

@@ -84,7 +84,7 @@ def test_create_archive():
     cfn_client.create_stack(StackName=stack_name, TemplateBody=template)
 
     # then
-    archive_arn = "arn:aws:events:eu-central-1:{0}:archive/{1}".format(ACCOUNT_ID, name)
+    archive_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/{name}"
     stack = cfn_client.describe_stacks(StackName=stack_name)["Stacks"][0]
     stack["Outputs"][0]["OutputValue"].should.equal(archive_arn)
 
@@ -119,7 +119,7 @@ def test_update_archive():
     response = events_client.describe_archive(ArchiveName=name)
 
     response["ArchiveArn"].should.equal(
-        "arn:aws:events:eu-central-1:{0}:archive/{1}".format(ACCOUNT_ID, name)
+        f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:archive/{name}"
     )
     response["Description"].should.equal("test archive")
 
@@ -156,7 +156,7 @@ def test_create_rule():
     cfn_client.create_stack(StackName=stack_name, TemplateBody=template)
 
     # then
-    rule_arn = "arn:aws:events:eu-central-1:{0}:rule/{1}".format(ACCOUNT_ID, name)
+    rule_arn = f"arn:aws:events:eu-central-1:{ACCOUNT_ID}:rule/{name}"
     stack = cfn_client.describe_stacks(StackName=stack_name)["Stacks"][0]
     stack["Outputs"][0]["OutputValue"].should.equal(rule_arn)
 

tests/test_events/test_events_integration.py

@@ -28,9 +28,7 @@ def test_send_to_cw_log_group():
         Targets=[
             {
                 "Id": "logs",
-                "Arn": "arn:aws:logs:eu-central-1:{0}:log-group:{1}".format(
+                "Arn": f"arn:aws:logs:eu-central-1:{ACCOUNT_ID}:log-group:{log_group_name}",
-                    ACCOUNT_ID, log_group_name
-                ),
             }
         ],
     )

tests/test_firehose/test_firehose_destination_types.py

@@ -16,7 +16,7 @@ def create_extended_s3_delivery_stream(client, stream_name):
         DeliveryStreamName=stream_name,
         DeliveryStreamType="DirectPut",
         ExtendedS3DestinationConfiguration={
-            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(ACCOUNT_ID),
+            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
             "BucketARN": "arn:aws:s3:::firehose-test",
             "Prefix": "myFolder/",
             "CompressionFormat": "UNCOMPRESSED",
@@ -28,9 +28,7 @@ def create_extended_s3_delivery_stream(client, stream_name):
                 },
                 "SchemaConfiguration": {
                     "DatabaseName": stream_name,
-                    "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                    "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                        ACCOUNT_ID
-                    ),
                     "TableName": "outputTable",
                 },
             },
@@ -43,7 +41,7 @@ def create_redshift_delivery_stream(client, stream_name):
     return client.create_delivery_stream(
         DeliveryStreamName=stream_name,
         RedshiftDestinationConfiguration={
-            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(ACCOUNT_ID),
+            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
             "ClusterJDBCURL": "jdbc:redshift://host.amazonaws.com:5439/database",
             "CopyCommand": {
                 "DataTableName": "outputTable",
@@ -52,9 +50,7 @@ def create_redshift_delivery_stream(client, stream_name):
             "Username": "username",
             "Password": "password",
             "S3Configuration": {
-                "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                    ACCOUNT_ID
-                ),
                 "BucketARN": "arn:aws:s3:::firehose-test",
                 "Prefix": "myFolder/",
                 "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
@@ -70,7 +66,7 @@ def create_elasticsearch_delivery_stream(client, stream_name):
         DeliveryStreamName=stream_name,
         DeliveryStreamType="DirectPut",
         ElasticsearchDestinationConfiguration={
-            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(ACCOUNT_ID),
+            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
             "DomainARN": "arn:aws:es:::domain/firehose-test",
             "IndexName": "myIndex",
             "TypeName": "UNCOMPRESSED",
@@ -78,9 +74,7 @@ def create_elasticsearch_delivery_stream(client, stream_name):
             "BufferingHints": {"IntervalInSeconds": 123, "SizeInMBs": 123},
             "RetryOptions": {"DurationInSeconds": 123},
             "S3Configuration": {
-                "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                    ACCOUNT_ID
-                ),
                 "BucketARN": "arn:aws:s3:::firehose-test",
                 "Prefix": "myFolder/",
                 "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
@@ -101,9 +95,7 @@ def create_http_delivery_stream(client, stream_name):
             "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
             "CloudWatchLoggingOptions": {"Enabled": False},
             "S3Configuration": {
-                "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                    ACCOUNT_ID
-                ),
                 "BucketARN": "arn:aws:s3:::firehose-test",
                 "Prefix": "myFolder/",
                 "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
@@ -140,9 +132,7 @@ def test_create_redshift_delivery_stream():
                 {
                     "DestinationId": "destinationId-000000000001",
                     "RedshiftDestinationDescription": {
-                        "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                        "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                            ACCOUNT_ID
-                        ),
                         "ClusterJDBCURL": "jdbc:redshift://host.amazonaws.com:5439/database",
                         "CopyCommand": {
                             "DataTableName": "outputTable",
@@ -150,9 +140,7 @@ def test_create_redshift_delivery_stream():
                         },
                         "Username": "username",
                         "S3DestinationDescription": {
-                            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                                ACCOUNT_ID
-                            ),
                             "BucketARN": "arn:aws:s3:::firehose-test",
                             "Prefix": "myFolder/",
                             "BufferingHints": {
@@ -196,9 +184,7 @@ def test_create_extended_s3_delivery_stream():
                 {
                     "DestinationId": "destinationId-000000000001",
                     "ExtendedS3DestinationDescription": {
-                        "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                        "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                            ACCOUNT_ID
-                        ),
                         "BucketARN": "arn:aws:s3:::firehose-test",
                         "Prefix": "myFolder/",
                         "CompressionFormat": "UNCOMPRESSED",
@@ -214,17 +200,13 @@ def test_create_extended_s3_delivery_stream():
                             },
                             "SchemaConfiguration": {
                                 "DatabaseName": stream_name,
-                                "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                                "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                                    ACCOUNT_ID
-                                ),
                                 "TableName": "outputTable",
                             },
                         },
                     },
                     "S3DestinationDescription": {
-                        "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                        "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                            ACCOUNT_ID
-                        ),
                         "BucketARN": "arn:aws:s3:::firehose-test",
                         "Prefix": "myFolder/",
                         "CompressionFormat": "UNCOMPRESSED",
@@ -263,9 +245,7 @@ def test_create_elasticsearch_delivery_stream():
                 {
                     "DestinationId": "destinationId-000000000001",
                     "ElasticsearchDestinationDescription": {
-                        "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                        "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                            ACCOUNT_ID
-                        ),
                         "DomainARN": "arn:aws:es:::domain/firehose-test",
                         "IndexName": "myIndex",
                         "TypeName": "UNCOMPRESSED",
@@ -273,9 +253,7 @@ def test_create_elasticsearch_delivery_stream():
                         "BufferingHints": {"IntervalInSeconds": 123, "SizeInMBs": 123},
                         "RetryOptions": {"DurationInSeconds": 123},
                         "S3DestinationDescription": {
-                            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                                ACCOUNT_ID
-                            ),
                             "BucketARN": "arn:aws:s3:::firehose-test",
                             "Prefix": "myFolder/",
                             "BufferingHints": {
@@ -301,7 +279,7 @@ def test_create_s3_delivery_stream():
     response = client.create_delivery_stream(
         DeliveryStreamName=stream_name,
         S3DestinationConfiguration={
-            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(ACCOUNT_ID),
+            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
             "BucketARN": "arn:aws:s3:::firehose-test",
             "Prefix": "myFolder/",
             "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
@@ -328,9 +306,7 @@ def test_create_s3_delivery_stream():
                 {
                     "DestinationId": "destinationId-000000000001",
                     "S3DestinationDescription": {
-                        "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                        "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                            ACCOUNT_ID
-                        ),
                         "BucketARN": "arn:aws:s3:::firehose-test",
                         "Prefix": "myFolder/",
                         "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
@@ -375,9 +351,7 @@ def test_create_http_stream():
                         "BufferingHints": {"SizeInMBs": 123, "IntervalInSeconds": 124},
                         "CloudWatchLoggingOptions": {"Enabled": False},
                         "S3DestinationDescription": {
-                            "RoleARN": "arn:aws:iam::{}:role/firehose_delivery_role".format(
+                            "RoleARN": f"arn:aws:iam::{ACCOUNT_ID}:role/firehose_delivery_role",
-                                ACCOUNT_ID
-                            ),
                             "BucketARN": "arn:aws:s3:::firehose-test",
                             "Prefix": "myFolder/",
                             "BufferingHints": {

tests/test_glue/helpers.py

@@ -15,9 +15,7 @@ from .fixtures.schema_registry import (
 def create_database_input(database_name):
     database_input = copy.deepcopy(DATABASE_INPUT)
     database_input["Name"] = database_name
-    database_input["LocationUri"] = "s3://my-bucket/{database_name}".format(
+    database_input["LocationUri"] = f"s3://my-bucket/{database_name}"
-        database_name=database_name
-    )
     return database_input
 
 
@@ -42,9 +40,7 @@ def create_table_input(database_name, table_name, columns=None, partition_keys=N
     table_input["StorageDescriptor"]["Columns"] = columns or []
     table_input["StorageDescriptor"][
         "Location"
-    ] = "s3://my-bucket/{database_name}/{table_name}".format(
+    ] = f"s3://my-bucket/{database_name}/{table_name}"
-        database_name=database_name, table_name=table_name
-    )
     return table_input
 
 
@@ -93,9 +89,7 @@ def create_column(name, type_, comment=None, parameters=None):
 
 
 def create_partition_input(database_name, table_name, values=None, columns=None):
-    root_path = "s3://my-bucket/{database_name}/{table_name}".format(
+    root_path = f"s3://my-bucket/{database_name}/{table_name}"
-        database_name=database_name, table_name=table_name
-    )
 
     part_input = copy.deepcopy(PARTITION_INPUT)
     part_input["Values"] = values or []

tests/test_glue/test_datacatalog.py

@@ -552,7 +552,7 @@ def test_batch_create_partition():
 
     partition_inputs = []
     for i in range(0, 20):
-        values = ["2018-10-{:2}".format(i)]
+        values = [f"2018-10-{i:2}"]
         part_input = helpers.create_partition_input(
             database_name, table_name, values=values
         )
@@ -994,7 +994,7 @@ def test_batch_delete_partition():
 
     partition_inputs = []
     for i in range(0, 20):
-        values = ["2018-10-{:2}".format(i)]
+        values = [f"2018-10-{i:2}"]
         part_input = helpers.create_partition_input(
             database_name, table_name, values=values
         )
@@ -1027,7 +1027,7 @@ def test_batch_delete_partition_with_bad_partitions():
 
     partition_inputs = []
     for i in range(0, 20):
-        values = ["2018-10-{:2}".format(i)]
+        values = [f"2018-10-{i:2}"]
         part_input = helpers.create_partition_input(
             database_name, table_name, values=values
         )

tests/test_iam/test_iam.py

@@ -514,7 +514,7 @@ def test_create_policy():
         PolicyName="TestCreatePolicy", PolicyDocument=MOCK_POLICY
     )
     response["Policy"]["Arn"].should.equal(
-        "arn:aws:iam::{}:policy/TestCreatePolicy".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicy"
     )
 
 
@@ -547,14 +547,12 @@ def test_create_policy_versions():
     conn = boto3.client("iam", region_name="us-east-1")
     with pytest.raises(ClientError):
         conn.create_policy_version(
-            PolicyArn="arn:aws:iam::{}:policy/TestCreatePolicyVersion".format(
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicyVersion",
-                ACCOUNT_ID
-            ),
             PolicyDocument='{"some":"policy"}',
         )
     conn.create_policy(PolicyName="TestCreatePolicyVersion", PolicyDocument=MOCK_POLICY)
     version = conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestCreatePolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicyVersion",
         PolicyDocument=MOCK_POLICY,
         SetAsDefault=True,
     )
@@ -562,11 +560,11 @@ def test_create_policy_versions():
     version.get("PolicyVersion").get("VersionId").should.equal("v2")
     version.get("PolicyVersion").get("IsDefaultVersion").should.be.ok
     conn.delete_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestCreatePolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicyVersion",
         VersionId="v1",
     )
     version = conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestCreatePolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicyVersion",
         PolicyDocument=MOCK_POLICY,
     )
     version.get("PolicyVersion").get("VersionId").should.equal("v3")
@@ -581,16 +579,12 @@ def test_create_many_policy_versions():
     )
     for _ in range(0, 4):
         conn.create_policy_version(
-            PolicyArn="arn:aws:iam::{}:policy/TestCreateManyPolicyVersions".format(
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreateManyPolicyVersions",
-                ACCOUNT_ID
-            ),
             PolicyDocument=MOCK_POLICY,
         )
     with pytest.raises(ClientError):
         conn.create_policy_version(
-            PolicyArn="arn:aws:iam::{}:policy/TestCreateManyPolicyVersions".format(
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreateManyPolicyVersions",
-                ACCOUNT_ID
-            ),
             PolicyDocument=MOCK_POLICY,
         )
 
@@ -602,23 +596,17 @@ def test_set_default_policy_version():
         PolicyName="TestSetDefaultPolicyVersion", PolicyDocument=MOCK_POLICY
     )
     conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion",
-            ACCOUNT_ID
-        ),
         PolicyDocument=MOCK_POLICY_2,
         SetAsDefault=True,
     )
     conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion",
-            ACCOUNT_ID
-        ),
         PolicyDocument=MOCK_POLICY_3,
         SetAsDefault=True,
     )
     versions = conn.list_policy_versions(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion"
-            ACCOUNT_ID
-        )
     )
     versions.get("Versions")[0].get("Document").should.equal(json.loads(MOCK_POLICY))
     versions.get("Versions")[0].get("IsDefaultVersion").shouldnt.be.ok
@@ -628,15 +616,11 @@ def test_set_default_policy_version():
     versions.get("Versions")[2].get("IsDefaultVersion").should.be.ok
 
     conn.set_default_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion",
-            ACCOUNT_ID
-        ),
         VersionId="v1",
     )
     versions = conn.list_policy_versions(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion"
-            ACCOUNT_ID
-        )
     )
     versions.get("Versions")[0].get("Document").should.equal(json.loads(MOCK_POLICY))
     versions.get("Versions")[0].get("IsDefaultVersion").should.be.ok
@@ -647,20 +631,16 @@ def test_set_default_policy_version():
 
     # Set default version for non-existing policy
     conn.set_default_policy_version.when.called_with(
-        PolicyArn="arn:aws:iam::{}:policy/TestNonExistingPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestNonExistingPolicy",
         VersionId="v1",
     ).should.throw(
         ClientError,
-        "Policy arn:aws:iam::{}:policy/TestNonExistingPolicy not found".format(
+        f"Policy arn:aws:iam::{ACCOUNT_ID}:policy/TestNonExistingPolicy not found",
-            ACCOUNT_ID
-        ),
     )
 
     # Set default version for incorrect version
     conn.set_default_policy_version.when.called_with(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion",
-            ACCOUNT_ID
-        ),
         VersionId="wrong_version_id",
     ).should.throw(
         ClientError,
@@ -669,15 +649,11 @@ def test_set_default_policy_version():
 
     # Set default version for non-existing version
     conn.set_default_policy_version.when.called_with(
-        PolicyArn="arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion",
-            ACCOUNT_ID
-        ),
         VersionId="v4",
     ).should.throw(
         ClientError,
-        "Policy arn:aws:iam::{}:policy/TestSetDefaultPolicyVersion version v4 does not exist or is not attachable.".format(
+        f"Policy arn:aws:iam::{ACCOUNT_ID}:policy/TestSetDefaultPolicyVersion version v4 does not exist or is not attachable.",
-            ACCOUNT_ID
-        ),
     )
 
 
@@ -686,10 +662,10 @@ def test_get_policy():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestGetPolicy", PolicyDocument=MOCK_POLICY)
     policy = conn.get_policy(
-        PolicyArn="arn:aws:iam::{}:policy/TestGetPolicy".format(ACCOUNT_ID)
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestGetPolicy"
     )
     policy["Policy"]["Arn"].should.equal(
-        "arn:aws:iam::{}:policy/TestGetPolicy".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:policy/TestGetPolicy"
     )
 
 
@@ -712,16 +688,16 @@ def test_get_policy_version():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestGetPolicyVersion", PolicyDocument=MOCK_POLICY)
     version = conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestGetPolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestGetPolicyVersion",
         PolicyDocument=MOCK_POLICY,
     )
     with pytest.raises(ClientError):
         conn.get_policy_version(
-            PolicyArn="arn:aws:iam::{}:policy/TestGetPolicyVersion".format(ACCOUNT_ID),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestGetPolicyVersion",
             VersionId="v2-does-not-exist",
         )
     retrieved = conn.get_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestGetPolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestGetPolicyVersion",
         VersionId=version.get("PolicyVersion").get("VersionId"),
     )
     retrieved.get("PolicyVersion").get("Document").should.equal(json.loads(MOCK_POLICY))
@@ -766,25 +742,25 @@ def test_list_policy_versions():
     conn = boto3.client("iam", region_name="us-east-1")
     with pytest.raises(ClientError):
         versions = conn.list_policy_versions(
-            PolicyArn="arn:aws:iam::{}:policy/TestListPolicyVersions".format(ACCOUNT_ID)
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestListPolicyVersions"
         )
     conn.create_policy(PolicyName="TestListPolicyVersions", PolicyDocument=MOCK_POLICY)
     versions = conn.list_policy_versions(
-        PolicyArn="arn:aws:iam::{}:policy/TestListPolicyVersions".format(ACCOUNT_ID)
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestListPolicyVersions"
     )
     versions.get("Versions")[0].get("VersionId").should.equal("v1")
     versions.get("Versions")[0].get("IsDefaultVersion").should.be.ok
 
     conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestListPolicyVersions".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestListPolicyVersions",
         PolicyDocument=MOCK_POLICY_2,
     )
     conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestListPolicyVersions".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestListPolicyVersions",
         PolicyDocument=MOCK_POLICY_3,
     )
     versions = conn.list_policy_versions(
-        PolicyArn="arn:aws:iam::{}:policy/TestListPolicyVersions".format(ACCOUNT_ID)
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestListPolicyVersions"
     )
     versions.get("Versions")[1].get("Document").should.equal(json.loads(MOCK_POLICY_2))
     versions.get("Versions")[1].get("IsDefaultVersion").shouldnt.be.ok
@@ -797,22 +773,20 @@ def test_delete_policy_version():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestDeletePolicyVersion", PolicyDocument=MOCK_POLICY)
     conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestDeletePolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestDeletePolicyVersion",
         PolicyDocument=MOCK_POLICY,
     )
     with pytest.raises(ClientError):
         conn.delete_policy_version(
-            PolicyArn="arn:aws:iam::{}:policy/TestDeletePolicyVersion".format(
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestDeletePolicyVersion",
-                ACCOUNT_ID
-            ),
             VersionId="v2-nope-this-does-not-exist",
         )
     conn.delete_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestDeletePolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestDeletePolicyVersion",
         VersionId="v2",
     )
     versions = conn.list_policy_versions(
-        PolicyArn="arn:aws:iam::{}:policy/TestDeletePolicyVersion".format(ACCOUNT_ID)
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestDeletePolicyVersion"
     )
     len(versions.get("Versions")).should.equal(1)
 
@@ -822,14 +796,12 @@ def test_delete_default_policy_version():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestDeletePolicyVersion", PolicyDocument=MOCK_POLICY)
     conn.create_policy_version(
-        PolicyArn="arn:aws:iam::{}:policy/TestDeletePolicyVersion".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestDeletePolicyVersion",
         PolicyDocument=MOCK_POLICY_2,
     )
     with pytest.raises(ClientError):
         conn.delete_policy_version(
-            PolicyArn="arn:aws:iam::{}:policy/TestDeletePolicyVersion".format(
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestDeletePolicyVersion",
-                ACCOUNT_ID
-            ),
             VersionId="v1",
         )
 
@@ -849,9 +821,7 @@ def test_create_policy_with_tags():
 
     # Get policy:
     policy = conn.get_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicyWithTags1"
-            ACCOUNT_ID, "TestCreatePolicyWithTags1"
-        )
     )["Policy"]
     assert len(policy["Tags"]) == 2
     assert policy["Tags"][0]["Key"] == "somekey"
@@ -872,9 +842,7 @@ def test_create_policy_with_empty_tag_value():
         Tags=[{"Key": "somekey", "Value": ""}],
     )
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestCreatePolicyWithTags2"
-            ACCOUNT_ID, "TestCreatePolicyWithTags2"
-        )
     )
     assert len(tags["Tags"]) == 1
     assert tags["Tags"][0]["Key"] == "somekey"
@@ -994,7 +962,7 @@ def test_create_policy_with_no_tags():
 
     # Get without tags:
     policy = conn.get_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy"
     )["Policy"]
     assert not policy.get("Tags")
 
@@ -1004,7 +972,7 @@ def test_get_policy_with_tags():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1013,7 +981,7 @@ def test_get_policy_with_tags():
 
     # Get policy:
     policy = conn.get_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy"
     )["Policy"]
     assert len(policy["Tags"]) == 2
     assert policy["Tags"][0]["Key"] == "somekey"
@@ -1027,7 +995,7 @@ def test_list_policy_tags():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1036,7 +1004,7 @@ def test_list_policy_tags():
 
     # List_policy_tags:
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy"
     )
     assert len(tags["Tags"]) == 2
     assert tags["Tags"][0]["Key"] == "somekey"
@@ -1052,7 +1020,7 @@ def test_list_policy_tags_pagination():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1061,7 +1029,7 @@ def test_list_policy_tags_pagination():
 
     # Test pagination:
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         MaxItems=1,
     )
     assert len(tags["Tags"]) == 1
@@ -1071,7 +1039,7 @@ def test_list_policy_tags_pagination():
     assert tags["Marker"] == "1"
 
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Marker=tags["Marker"],
     )
     assert len(tags["Tags"]) == 1
@@ -1086,7 +1054,7 @@ def test_updating_existing_tag():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1095,11 +1063,11 @@ def test_updating_existing_tag():
 
     # Test updating an existing tag:
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[{"Key": "somekey", "Value": "somenewvalue"}],
     )
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy"
     )
     assert len(tags["Tags"]) == 2
     assert tags["Tags"][0]["Key"] == "somekey"
@@ -1111,7 +1079,7 @@ def test_updating_existing_tag_with_empty_value():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1120,11 +1088,11 @@ def test_updating_existing_tag_with_empty_value():
 
     # Empty is good:
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[{"Key": "somekey", "Value": ""}],
     )
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy"
     )
     assert len(tags["Tags"]) == 2
     assert tags["Tags"][0]["Key"] == "somekey"
@@ -1136,7 +1104,7 @@ def test_updating_existing_tagged_policy_with_too_many_tags():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1149,7 +1117,7 @@ def test_updating_existing_tagged_policy_with_too_many_tags():
             map(lambda x: {"Key": str(x), "Value": str(x)}, range(0, 51))
         )
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
             Tags=too_many_tags,
         )
     assert (
@@ -1163,7 +1131,7 @@ def test_updating_existing_tagged_policy_with_duplicate_tag():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1173,7 +1141,7 @@ def test_updating_existing_tagged_policy_with_duplicate_tag():
     # With a duplicate tag:
     with pytest.raises(ClientError) as ce:
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
             Tags=[{"Key": "0", "Value": ""}, {"Key": "0", "Value": ""}],
         )
     assert (
@@ -1187,7 +1155,7 @@ def test_updating_existing_tagged_policy_with_duplicate_tag_different_casing():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1197,7 +1165,7 @@ def test_updating_existing_tagged_policy_with_duplicate_tag_different_casing():
     # Duplicate tag with different casing:
     with pytest.raises(ClientError) as ce:
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
             Tags=[{"Key": "a", "Value": ""}, {"Key": "A", "Value": ""}],
         )
     assert (
@@ -1211,7 +1179,7 @@ def test_updating_existing_tagged_policy_with_large_key():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1221,7 +1189,7 @@ def test_updating_existing_tagged_policy_with_large_key():
     # With a really big key:
     with pytest.raises(ClientError) as ce:
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
             Tags=[{"Key": "0" * 129, "Value": ""}],
         )
     assert (
@@ -1235,7 +1203,7 @@ def test_updating_existing_tagged_policy_with_large_value():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1245,7 +1213,7 @@ def test_updating_existing_tagged_policy_with_large_value():
     # With a really big value:
     with pytest.raises(ClientError) as ce:
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
             Tags=[{"Key": "0", "Value": "0" * 257}],
         )
     assert (
@@ -1259,7 +1227,7 @@ def test_updating_existing_tagged_policy_with_invalid_character():
     conn = boto3.client("iam", region_name="us-east-1")
     conn.create_policy(PolicyName="TestTagPolicy", PolicyDocument=MOCK_POLICY)
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1269,7 +1237,7 @@ def test_updating_existing_tagged_policy_with_invalid_character():
     # With an invalid character:
     with pytest.raises(ClientError) as ce:
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestTagPolicy",
             Tags=[{"Key": "NOWAY!", "Value": ""}],
         )
     assert (
@@ -1285,7 +1253,7 @@ def test_tag_non_existant_policy():
     # With a policy that doesn't exist:
     with pytest.raises(ClientError):
         conn.tag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "NotAPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/NotAPolicy",
             Tags=[{"Key": "some", "Value": "value"}],
         )
 
@@ -1297,7 +1265,7 @@ def test_untag_policy():
 
     # With proper tag values:
     conn.tag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy",
         Tags=[
             {"Key": "somekey", "Value": "somevalue"},
             {"Key": "someotherkey", "Value": "someothervalue"},
@@ -1306,11 +1274,11 @@ def test_untag_policy():
 
     # Remove them:
     conn.untag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy",
         TagKeys=["somekey"],
     )
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy"
     )
     assert len(tags["Tags"]) == 1
     assert tags["Tags"][0]["Key"] == "someotherkey"
@@ -1318,11 +1286,11 @@ def test_untag_policy():
 
     # And again:
     conn.untag_policy(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy"),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy",
         TagKeys=["someotherkey"],
     )
     tags = conn.list_policy_tags(
-        PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy")
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy"
     )
     assert not tags["Tags"]
 
@@ -1330,7 +1298,7 @@ def test_untag_policy():
     # With more than 50 tags:
     with pytest.raises(ClientError) as ce:
         conn.untag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy",
             TagKeys=[str(x) for x in range(0, 51)],
         )
     assert (
@@ -1342,7 +1310,7 @@ def test_untag_policy():
     # With a really big key:
     with pytest.raises(ClientError) as ce:
         conn.untag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy",
             TagKeys=["0" * 129],
         )
     assert (
@@ -1354,7 +1322,7 @@ def test_untag_policy():
     # With an invalid character:
     with pytest.raises(ClientError) as ce:
         conn.untag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "TestUnTagPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/TestUnTagPolicy",
             TagKeys=["NOWAY!"],
         )
     assert (
@@ -1366,7 +1334,7 @@ def test_untag_policy():
     # With a policy that doesn't exist:
     with pytest.raises(ClientError):
         conn.untag_policy(
-            PolicyArn="arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, "NotAPolicy"),
+            PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/NotAPolicy",
             TagKeys=["somevalue"],
         )
 
@@ -1378,7 +1346,7 @@ def test_create_user_boto():
     u["Path"].should.equal("/")
     u["UserName"].should.equal("my-user")
     u.should.have.key("UserId")
-    u["Arn"].should.equal("arn:aws:iam::{}:user/my-user".format(ACCOUNT_ID))
+    u["Arn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:user/my-user")
     u["CreateDate"].should.be.a(datetime)
 
     with pytest.raises(ClientError) as ex:
@@ -1403,7 +1371,7 @@ def test_get_user():
     u["Path"].should.equal("/")
     u["UserName"].should.equal("my-user")
     u.should.have.key("UserId")
-    u["Arn"].should.equal("arn:aws:iam::{}:user/my-user".format(ACCOUNT_ID))
+    u["Arn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:user/my-user")
     u["CreateDate"].should.be.a(datetime)
 
 
@@ -1438,7 +1406,7 @@ def test_list_users():
     user = response["Users"][0]
     user["UserName"].should.equal("my-user")
     user["Path"].should.equal("/")
-    user["Arn"].should.equal("arn:aws:iam::{}:user/my-user".format(ACCOUNT_ID))
+    user["Arn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:user/my-user")
     response["IsTruncated"].should.equal(False)
 
     conn.create_user(UserName="my-user-1", Path="myUser")
@@ -1620,9 +1588,7 @@ def test_create_virtual_mfa_device():
     response = client.create_virtual_mfa_device(VirtualMFADeviceName="test-device")
     device = response["VirtualMFADevice"]
 
-    device["SerialNumber"].should.equal(
+    device["SerialNumber"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:mfa/test-device")
-        "arn:aws:iam::{}:mfa/test-device".format(ACCOUNT_ID)
-    )
     device["Base32StringSeed"].decode("ascii").should.match("[A-Z234567]")
     device["QRCodePNG"].should_not.equal("")
 
@@ -1631,9 +1597,7 @@ def test_create_virtual_mfa_device():
     )
     device = response["VirtualMFADevice"]
 
-    device["SerialNumber"].should.equal(
+    device["SerialNumber"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:mfa/test-device-2")
-        "arn:aws:iam::{}:mfa/test-device-2".format(ACCOUNT_ID)
-    )
     device["Base32StringSeed"].decode("ascii").should.match("[A-Z234567]")
     device["QRCodePNG"].should_not.equal("")
 
@@ -1643,7 +1607,7 @@ def test_create_virtual_mfa_device():
     device = response["VirtualMFADevice"]
 
     device["SerialNumber"].should.equal(
-        "arn:aws:iam::{}:mfa/test/test-device".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:mfa/test/test-device"
     )
     device["Base32StringSeed"].decode("ascii").should.match("[A-Z234567]")
     device["QRCodePNG"].should_not.equal("")
@@ -1677,7 +1641,7 @@ def test_create_virtual_mfa_device_errors():
         "It must begin and end with / and contain only alphanumeric characters and/or / characters.",
     )
 
-    too_long_path = "/{}/".format("b" * 511)
+    too_long_path = f"/{('b' * 511)}/"
     client.create_virtual_mfa_device.when.called_with(
         Path=too_long_path, VirtualMFADeviceName="test-device"
     ).should.throw(
@@ -1706,12 +1670,12 @@ def test_delete_virtual_mfa_device():
 def test_delete_virtual_mfa_device_errors():
     client = boto3.client("iam", region_name="us-east-1")
 
-    serial_number = "arn:aws:iam::{}:mfa/not-existing".format(ACCOUNT_ID)
+    serial_number = f"arn:aws:iam::{ACCOUNT_ID}:mfa/not-existing"
     client.delete_virtual_mfa_device.when.called_with(
         SerialNumber=serial_number
     ).should.throw(
         ClientError,
-        "VirtualMFADevice with serial number {0} doesn't exist.".format(serial_number),
+        f"VirtualMFADevice with serial number {serial_number} doesn't exist.",
     )
 
 
@@ -1796,9 +1760,7 @@ def test_enable_virtual_mfa_device():
     device["User"]["Path"].should.equal("/")
     device["User"]["UserName"].should.equal("test-user")
     device["User"]["UserId"].should.match("[a-z0-9]+")
-    device["User"]["Arn"].should.equal(
+    device["User"]["Arn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:user/test-user")
-        "arn:aws:iam::{}:user/test-user".format(ACCOUNT_ID)
-    )
     device["User"]["CreateDate"].should.be.a(datetime)
     device["User"]["Tags"].should.equal(tags)
     device["EnableDate"].should.be.a(datetime)
@@ -2324,7 +2286,7 @@ def test_get_account_authorization_details():
     )
 
     conn = boto3.client("iam", region_name="us-east-1")
-    boundary = "arn:aws:iam::{}:policy/boundary".format(ACCOUNT_ID)
+    boundary = f"arn:aws:iam::{ACCOUNT_ID}:policy/boundary"
     conn.create_role(
         RoleName="my-role",
         AssumeRolePolicyDocument="some policy",
@@ -2351,11 +2313,11 @@ def test_get_account_authorization_details():
 
     conn.attach_user_policy(
         UserName="testUser",
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
     )
     conn.attach_group_policy(
         GroupName="testGroup",
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
     )
 
     conn.add_user_to_group(UserName="testUser", GroupName="testGroup")
@@ -2375,7 +2337,7 @@ def test_get_account_authorization_details():
     )
     conn.attach_role_policy(
         RoleName="my-role",
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
     )
 
     result = conn.get_account_authorization_details(Filter=["Role"])
@@ -2392,7 +2354,7 @@ def test_get_account_authorization_details():
         "PermissionsBoundary"
     ] == {
         "PermissionsBoundaryType": "PermissionsBoundaryPolicy",
-        "PermissionsBoundaryArn": "arn:aws:iam::{}:policy/boundary".format(ACCOUNT_ID),
+        "PermissionsBoundaryArn": f"arn:aws:iam::{ACCOUNT_ID}:policy/boundary",
     }
     assert len(result["RoleDetailList"][0]["Tags"]) == 2
     assert len(result["RoleDetailList"][0]["RolePolicyList"]) == 1
@@ -2401,9 +2363,10 @@ def test_get_account_authorization_details():
         result["RoleDetailList"][0]["AttachedManagedPolicies"][0]["PolicyName"]
         == "testPolicy"
     )
-    assert result["RoleDetailList"][0]["AttachedManagedPolicies"][0][
+    assert (
-        "PolicyArn"
+        result["RoleDetailList"][0]["AttachedManagedPolicies"][0]["PolicyArn"]
-    ] == "arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID)
+        == f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy"
+    )
     assert result["RoleDetailList"][0]["RolePolicyList"][0][
         "PolicyDocument"
     ] == json.loads(test_policy)
@@ -2420,9 +2383,10 @@ def test_get_account_authorization_details():
         result["UserDetailList"][0]["AttachedManagedPolicies"][0]["PolicyName"]
         == "testPolicy"
     )
-    assert result["UserDetailList"][0]["AttachedManagedPolicies"][0][
+    assert (
-        "PolicyArn"
+        result["UserDetailList"][0]["AttachedManagedPolicies"][0]["PolicyArn"]
-    ] == "arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID)
+        == f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy"
+    )
     assert result["UserDetailList"][0]["UserPolicyList"][0][
         "PolicyDocument"
     ] == json.loads(test_policy)
@@ -2438,9 +2402,10 @@ def test_get_account_authorization_details():
         result["GroupDetailList"][0]["AttachedManagedPolicies"][0]["PolicyName"]
         == "testPolicy"
     )
-    assert result["GroupDetailList"][0]["AttachedManagedPolicies"][0][
+    assert (
-        "PolicyArn"
+        result["GroupDetailList"][0]["AttachedManagedPolicies"][0]["PolicyArn"]
-    ] == "arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID)
+        == f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy"
+    )
     assert result["GroupDetailList"][0]["GroupPolicyList"][0][
         "PolicyDocument"
     ] == json.loads(test_policy)
@@ -2508,14 +2473,16 @@ def test_signing_certs():
             UserName="notauser", CertificateId=cert_id, Status="Inactive"
         )
 
+    fake_id_name = "x" * 32
     with pytest.raises(ClientError) as ce:
         client.update_signing_certificate(
-            UserName="testing", CertificateId="x" * 32, Status="Inactive"
+            UserName="testing", CertificateId=fake_id_name, Status="Inactive"
         )
 
-    assert ce.value.response["Error"][
+    assert (
-        "Message"
+        ce.value.response["Error"]["Message"]
-    ] == "The Certificate with id {id} cannot be found.".format(id="x" * 32)
+        == f"The Certificate with id {fake_id_name} cannot be found."
+    )
 
     # List the certs:
     resp = client.list_signing_certificates(UserName="testing")["Certificates"]
@@ -2540,7 +2507,7 @@ def test_create_saml_provider():
         Name="TestSAMLProvider", SAMLMetadataDocument="a" * 1024
     )
     response["SAMLProviderArn"].should.equal(
-        "arn:aws:iam::{}:saml-provider/TestSAMLProvider".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:saml-provider/TestSAMLProvider"
     )
 
 
@@ -2562,7 +2529,7 @@ def test_list_saml_providers():
     conn.create_saml_provider(Name="TestSAMLProvider", SAMLMetadataDocument="a" * 1024)
     response = conn.list_saml_providers()
     response["SAMLProviderList"][0]["Arn"].should.equal(
-        "arn:aws:iam::{}:saml-provider/TestSAMLProvider".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:saml-provider/TestSAMLProvider"
     )
 
 
@@ -2583,9 +2550,10 @@ def test_delete_saml_provider():
     with pytest.raises(ClientError) as ce:
         conn.delete_signing_certificate(UserName="testing", CertificateId=cert_id)
 
-    assert ce.value.response["Error"][
+    assert (
-        "Message"
+        ce.value.response["Error"]["Message"]
-    ] == "The Certificate with id {id} cannot be found.".format(id=cert_id)
+        == f"The Certificate with id {cert_id} cannot be found."
+    )
 
     # Verify that it's not in the list:
     resp = conn.list_signing_certificates(UserName="testing")
@@ -2989,11 +2957,11 @@ def test_list_entities_for_policy():
 
     conn.attach_user_policy(
         UserName="testUser",
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
     )
     conn.attach_group_policy(
         GroupName="testGroup",
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
     )
 
     conn.add_user_to_group(UserName="testUser", GroupName="testGroup")
@@ -3013,11 +2981,11 @@ def test_list_entities_for_policy():
     )
     conn.attach_role_policy(
         RoleName="my-role",
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
     )
 
     response = conn.list_entities_for_policy(
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
         EntityFilter="Role",
     )
     assert response["PolicyRoles"][0]["RoleName"] == "my-role"
@@ -3026,7 +2994,7 @@ def test_list_entities_for_policy():
     response["PolicyUsers"].should.equal([])
 
     response = conn.list_entities_for_policy(
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
         EntityFilter="User",
     )
     assert response["PolicyUsers"][0]["UserName"] == "testUser"
@@ -3035,7 +3003,7 @@ def test_list_entities_for_policy():
     response["PolicyRoles"].should.equal([])
 
     response = conn.list_entities_for_policy(
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
         EntityFilter="Group",
     )
     assert response["PolicyGroups"][0]["GroupName"] == "testGroup"
@@ -3044,7 +3012,7 @@ def test_list_entities_for_policy():
     response["PolicyUsers"].should.equal([])
 
     response = conn.list_entities_for_policy(
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID),
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy",
         EntityFilter="LocalManagedPolicy",
     )
     assert response["PolicyGroups"][0]["GroupName"] == "testGroup"
@@ -3057,7 +3025,7 @@ def test_list_entities_for_policy():
 
     # Return everything when no entity is specified
     response = conn.list_entities_for_policy(
-        PolicyArn="arn:aws:iam::{}:policy/testPolicy".format(ACCOUNT_ID)
+        PolicyArn=f"arn:aws:iam::{ACCOUNT_ID}:policy/testPolicy"
     )
     response["PolicyGroups"][0]["GroupName"].should.equal("testGroup")
     response["PolicyUsers"][0]["UserName"].should.equal("testUser")
@@ -3074,9 +3042,7 @@ def test_create_role_no_path():
     resp = conn.create_role(
         RoleName="my-role", AssumeRolePolicyDocument="some policy", Description="test"
     )
-    resp.get("Role").get("Arn").should.equal(
+    resp.get("Role").get("Arn").should.equal(f"arn:aws:iam::{ACCOUNT_ID}:role/my-role")
-        "arn:aws:iam::{}:role/my-role".format(ACCOUNT_ID)
-    )
     resp.get("Role").should_not.have.key("PermissionsBoundary")
     resp.get("Role").get("Description").should.equal("test")
 
@@ -3084,7 +3050,7 @@ def test_create_role_no_path():
 @mock_iam()
 def test_create_role_with_permissions_boundary():
     conn = boto3.client("iam", region_name="us-east-1")
-    boundary = "arn:aws:iam::{}:policy/boundary".format(ACCOUNT_ID)
+    boundary = f"arn:aws:iam::{ACCOUNT_ID}:policy/boundary"
     resp = conn.create_role(
         RoleName="my-role",
         AssumeRolePolicyDocument="some policy",
@@ -3139,7 +3105,7 @@ def test_create_role_with_same_name_should_fail():
         )
     err.value.response["Error"]["Code"].should.equal("EntityAlreadyExists")
     err.value.response["Error"]["Message"].should.equal(
-        "Role with name {0} already exists.".format(test_role_name)
+        f"Role with name {test_role_name} already exists."
     )
 
 
@@ -3153,9 +3119,7 @@ def test_create_policy_with_same_name_should_fail():
         iam.create_policy(PolicyName=test_policy_name, PolicyDocument=MOCK_POLICY)
     err.value.response["Error"]["Code"].should.equal("EntityAlreadyExists")
     err.value.response["Error"]["Message"].should.equal(
-        "A policy called {0} already exists. Duplicate names are not allowed.".format(
+        f"A policy called {test_policy_name} already exists. Duplicate names are not allowed."
-            test_policy_name
-        )
     )
 
 
@@ -3237,7 +3201,7 @@ def test_get_account_password_policy_errors():
 
     client.get_account_password_policy.when.called_with().should.throw(
         ClientError,
-        "The Password Policy with domain name {} cannot be found.".format(ACCOUNT_ID),
+        f"The Password Policy with domain name {ACCOUNT_ID} cannot be found.",
     )
 
 
@@ -3254,7 +3218,7 @@ def test_delete_account_password_policy():
 
     client.get_account_password_policy.when.called_with().should.throw(
         ClientError,
-        "The Password Policy with domain name {} cannot be found.".format(ACCOUNT_ID),
+        f"The Password Policy with domain name {ACCOUNT_ID} cannot be found.",
     )
 
 
@@ -3467,11 +3431,11 @@ def test_role_list_config_discovered_resources():
         this_role = role_config_query.backends[DEFAULT_ACCOUNT_ID][
             "global"
         ].create_role(
-            role_name="role{}".format(ix),
+            role_name=f"role{ix}",
             assume_role_policy_document=None,
             path="/",
             permissions_boundary=None,
-            description="role{}".format(ix),
+            description=f"role{ix}",
             tags=[{"Key": "foo", "Value": "bar"}],
             max_session_duration=3600,
         )
@@ -3848,9 +3812,9 @@ def test_role_config_client():
     num_roles = 10
     for ix in range(1, num_roles + 1):
         this_policy = iam_client.create_role(
-            RoleName="role{}".format(ix),
+            RoleName=f"role{ix}",
             Path="/",
-            Description="role{}".format(ix),
+            Description=f"role{ix}",
             AssumeRolePolicyDocument=json.dumps("{ }"),
         )
         roles.append(
@@ -4075,10 +4039,10 @@ def test_policy_list_config_discovered_resources():
         this_policy = policy_config_query.backends[DEFAULT_ACCOUNT_ID][
             "global"
         ].create_policy(
-            description="policy{}".format(ix),
+            description=f"policy{ix}",
             path="",
             policy_document=json.dumps(basic_policy),
-            policy_name="policy{}".format(ix),
+            policy_name=f"policy{ix}",
             tags=[],
         )
         policies.append({"id": this_policy.id, "name": this_policy.name})
@@ -4301,10 +4265,10 @@ def test_policy_config_client():
     num_policies = 10
     for ix in range(1, num_policies + 1):
         this_policy = iam_client.create_policy(
-            PolicyName="policy{}".format(ix),
+            PolicyName=f"policy{ix}",
             Path="/",
             PolicyDocument=json.dumps(basic_policy),
-            Description="policy{}".format(ix),
+            Description=f"policy{ix}",
         )
         policies.append(
             {
@@ -4479,7 +4443,7 @@ def test_list_roles_with_more_than_100_roles_no_max_items_defaults_to_100():
     iam = boto3.client("iam", region_name="us-east-1")
     for i in range(150):
         iam.create_role(
-            RoleName="test_role_{}".format(i), AssumeRolePolicyDocument="some policy"
+            RoleName=f"test_role_{i}", AssumeRolePolicyDocument="some policy"
         )
     response = iam.list_roles()
     roles = response["Roles"]
@@ -4493,7 +4457,7 @@ def test_list_roles_max_item_and_marker_values_adhered():
     iam = boto3.client("iam", region_name="us-east-1")
     for i in range(10):
         iam.create_role(
-            RoleName="test_role_{}".format(i), AssumeRolePolicyDocument="some policy"
+            RoleName=f"test_role_{i}", AssumeRolePolicyDocument="some policy"
         )
     response = iam.list_roles(MaxItems=2)
     roles = response["Roles"]
@@ -4633,7 +4597,7 @@ def test_tag_user_error_unknown_user_name():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(404)
     ex.response["Error"]["Code"].should.contain("NoSuchEntity")
     ex.response["Error"]["Message"].should.equal(
-        "The user with name {} cannot be found.".format(name)
+        f"The user with name {name} cannot be found."
     )
 
 
@@ -4671,7 +4635,7 @@ def test_untag_user_error_unknown_user_name():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(404)
     ex.response["Error"]["Code"].should.contain("NoSuchEntity")
     ex.response["Error"]["Message"].should.equal(
-        "The user with name {} cannot be found.".format(name)
+        f"The user with name {name} cannot be found."
     )
 
 

tests/test_iam/test_iam_cloudformation.py

@@ -368,7 +368,7 @@ Resources:
 
     policy_arn = provisioned_resource["PhysicalResourceId"]
     policy_arn.should.match(
-        "arn:aws:iam::{}:policy/MyStack-ThePolicy-[A-Z0-9]+".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:policy/MyStack-ThePolicy-[A-Z0-9]+"
     )
     expected_name = policy_arn.split("/")[1]
 
@@ -420,7 +420,7 @@ Resources:
     logical_resource_id.should.equal("ThePolicy")
 
     policy_arn = provisioned_resource["PhysicalResourceId"]
-    policy_arn.should.equal("arn:aws:iam::{}:policy/{}".format(ACCOUNT_ID, name))
+    policy_arn.should.equal(f"arn:aws:iam::{ACCOUNT_ID}:policy/{name}")
 
     policy = iam_client.get_policy(PolicyArn=policy_arn)["Policy"]
     policy.should.have.key("Arn").equal(policy_arn)
@@ -469,7 +469,7 @@ Resources:
 
     policy_arn = provisioned_resource["PhysicalResourceId"]
     policy_arn.should.match(
-        "rn:aws:iam::{}:policy/MyStack-ThePolicy-[A-Z0-9]+".format(ACCOUNT_ID)
+        f"rn:aws:iam::{ACCOUNT_ID}:policy/MyStack-ThePolicy-[A-Z0-9]+"
     )
 
     response = iam_client.list_entities_for_policy(PolicyArn=policy_arn)
@@ -520,7 +520,7 @@ Resources:
 
     policy_arn = provisioned_resource["PhysicalResourceId"]
     policy_arn.should.match(
-        "rn:aws:iam::{}:policy/MyStack-ThePolicy-[A-Z0-9]+".format(ACCOUNT_ID)
+        f"rn:aws:iam::{ACCOUNT_ID}:policy/MyStack-ThePolicy-[A-Z0-9]+"
     )
 
     response = iam_client.list_entities_for_policy(PolicyArn=policy_arn)
@@ -571,7 +571,7 @@ Resources:
 
     policy_arn = provisioned_resource["PhysicalResourceId"]
     policy_arn.should.match(
-        "rn:aws:iam::{}:policy/MyStack-ThePolicy-[A-Z0-9]+".format(ACCOUNT_ID)
+        f"rn:aws:iam::{ACCOUNT_ID}:policy/MyStack-ThePolicy-[A-Z0-9]+"
     )
 
     response = iam_client.list_entities_for_policy(PolicyArn=policy_arn)
@@ -594,7 +594,7 @@ def test_iam_cloudformation_create_user_policy():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -646,7 +646,7 @@ def test_iam_cloudformation_update_user_policy():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -733,7 +733,7 @@ def test_iam_cloudformation_delete_user_policy_having_generated_name():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -788,7 +788,7 @@ def test_iam_cloudformation_create_role_policy():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -840,7 +840,7 @@ def test_iam_cloudformation_update_role_policy():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -927,7 +927,7 @@ def test_iam_cloudformation_delete_role_policy_having_generated_name():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -982,7 +982,7 @@ def test_iam_cloudformation_create_group_policy():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -1034,7 +1034,7 @@ def test_iam_cloudformation_update_group_policy():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"
@@ -1121,7 +1121,7 @@ def test_iam_cloudformation_delete_group_policy_having_generated_name():
     s3_client = boto3.client("s3", region_name="us-east-1")
     bucket_name = "my-bucket"
     s3_client.create_bucket(Bucket=bucket_name)
-    bucket_arn = "arn:aws:s3:::{0}".format(bucket_name)
+    bucket_arn = f"arn:aws:s3:::{bucket_name}"
 
     cf_client = boto3.client("cloudformation", region_name="us-east-1")
     stack_name = "MyStack"

tests/test_iam/test_iam_groups.py

@@ -40,7 +40,7 @@ def test_get_group_boto3():
     created["Path"].should.equal("/")
     created["GroupName"].should.equal("my-group")
     created.should.have.key("GroupId")
-    created["Arn"].should.equal("arn:aws:iam::{}:group/my-group".format(ACCOUNT_ID))
+    created["Arn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:group/my-group")
     created["CreateDate"].should.be.a(datetime)
 
     retrieved = conn.get_group(GroupName="my-group")["Group"]
@@ -63,15 +63,16 @@ def test_get_group_current():
     assert result["Group"]["GroupName"] == "my-group"
     assert isinstance(result["Group"]["CreateDate"], datetime)
     assert result["Group"]["GroupId"]
-    assert result["Group"]["Arn"] == "arn:aws:iam::{}:group/my-group".format(ACCOUNT_ID)
+    assert result["Group"]["Arn"] == f"arn:aws:iam::{ACCOUNT_ID}:group/my-group"
     assert not result["Users"]
 
     # Make a group with a different path:
     other_group = conn.create_group(GroupName="my-other-group", Path="some/location")
     assert other_group["Group"]["Path"] == "some/location"
-    assert other_group["Group"][
+    assert (
-        "Arn"
+        other_group["Group"]["Arn"]
-    ] == "arn:aws:iam::{}:group/some/location/my-other-group".format(ACCOUNT_ID)
+        == f"arn:aws:iam::{ACCOUNT_ID}:group/some/location/my-other-group"
+    )
 
 
 @mock_iam

tests/test_iam/test_iam_oidc.py

@@ -18,7 +18,7 @@ def test_create_open_id_connect_provider():
     )
 
     response["OpenIDConnectProviderArn"].should.equal(
-        "arn:aws:iam::{}:oidc-provider/example.com".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:oidc-provider/example.com"
     )
 
     response = client.create_open_id_connect_provider(
@@ -26,7 +26,7 @@ def test_create_open_id_connect_provider():
     )
 
     response["OpenIDConnectProviderArn"].should.equal(
-        "arn:aws:iam::{}:oidc-provider/example.org".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:oidc-provider/example.org"
     )
 
     response = client.create_open_id_connect_provider(
@@ -34,7 +34,7 @@ def test_create_open_id_connect_provider():
     )
 
     response["OpenIDConnectProviderArn"].should.equal(
-        "arn:aws:iam::{}:oidc-provider/example.org/oidc".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:oidc-provider/example.org/oidc"
     )
 
     response = client.create_open_id_connect_provider(
@@ -42,7 +42,7 @@ def test_create_open_id_connect_provider():
     )
 
     response["OpenIDConnectProviderArn"].should.equal(
-        "arn:aws:iam::{}:oidc-provider/example.org/oidc-query".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:oidc-provider/example.org/oidc-query"
     )
 
 
@@ -106,7 +106,7 @@ def test_create_open_id_connect_provider_too_many_entries():
 def test_create_open_id_connect_provider_quota_error():
     client = boto3.client("iam", region_name="us-east-1")
 
-    too_many_client_ids = ["{}".format(i) for i in range(101)]
+    too_many_client_ids = [f"{i}" for i in range(101)]
     with pytest.raises(ClientError) as e:
         client.create_open_id_connect_provider(
             Url="http://example.org",
@@ -155,7 +155,7 @@ def test_delete_open_id_connect_provider():
     client.get_open_id_connect_provider.when.called_with(
         OpenIDConnectProviderArn=open_id_arn
     ).should.throw(
-        ClientError, "OpenIDConnect Provider not found for arn {}".format(open_id_arn)
+        ClientError, f"OpenIDConnect Provider not found for arn {open_id_arn}"
     )
 
     # deleting a non existing provider should be successful
@@ -206,13 +206,11 @@ def test_get_open_id_connect_provider_errors():
     )
     open_id_arn = response["OpenIDConnectProviderArn"]
 
+    unknown_arn = open_id_arn + "-not-existing"
     client.get_open_id_connect_provider.when.called_with(
-        OpenIDConnectProviderArn=open_id_arn + "-not-existing"
+        OpenIDConnectProviderArn=unknown_arn
     ).should.throw(
-        ClientError,
+        ClientError, f"OpenIDConnect Provider not found for arn {unknown_arn}"
-        "OpenIDConnect Provider not found for arn {}".format(
-            open_id_arn + "-not-existing"
-        ),
     )
 
 

tests/test_iam/test_iam_server_certificates.py

@@ -22,9 +22,7 @@ def test_get_all_server_certs():
     certs.should.have.length_of(1)
     cert1 = certs[0]
     cert1["ServerCertificateName"].should.equal("certname")
-    cert1["Arn"].should.equal(
+    cert1["Arn"].should.equal(f"arn:aws:iam::{ACCOUNT_ID}:server-certificate/certname")
-        "arn:aws:iam::{}:server-certificate/certname".format(ACCOUNT_ID)
-    )
 
 
 @mock_iam
@@ -59,7 +57,7 @@ def test_get_server_cert():
     metadata["Path"].should.equal("/")
     metadata["ServerCertificateName"].should.equal("certname")
     metadata["Arn"].should.equal(
-        "arn:aws:iam::{}:server-certificate/certname".format(ACCOUNT_ID)
+        f"arn:aws:iam::{ACCOUNT_ID}:server-certificate/certname"
     )
     metadata.should.have.key("ServerCertificateId")
     metadata["UploadDate"].should.be.a(datetime)

tests/test_iot/test_iot.py

@@ -16,25 +16,25 @@ def test_endpoints():
     endpoint = client.describe_endpoint(endpointType="iot:Data")
     endpoint.should.have.key("endpointAddress").which.should_not.contain("ats")
     endpoint.should.have.key("endpointAddress").which.should.contain(
-        "iot.{}.amazonaws.com".format(region_name)
+        f"iot.{region_name}.amazonaws.com"
     )
 
     # iot:Data-ATS
     endpoint = client.describe_endpoint(endpointType="iot:Data-ATS")
     endpoint.should.have.key("endpointAddress").which.should.contain(
-        "ats.iot.{}.amazonaws.com".format(region_name)
+        f"ats.iot.{region_name}.amazonaws.com"
     )
 
     # iot:Data-ATS
     endpoint = client.describe_endpoint(endpointType="iot:CredentialProvider")
     endpoint.should.have.key("endpointAddress").which.should.contain(
-        "credentials.iot.{}.amazonaws.com".format(region_name)
+        f"credentials.iot.{region_name}.amazonaws.com"
     )
 
     # iot:Data-ATS
     endpoint = client.describe_endpoint(endpointType="iot:Jobs")
     endpoint.should.have.key("endpointAddress").which.should.contain(
-        "jobs.iot.{}.amazonaws.com".format(region_name)
+        f"jobs.iot.{region_name}.amazonaws.com"
     )
 
     # raise InvalidRequestException

tests/test_iot/test_iot_certificates.py

@@ -206,7 +206,7 @@ def test_delete_certificate_validation():
     with pytest.raises(ClientError) as e:
         client.delete_certificate(certificateId=cert_id)
     e.value.response["Error"]["Message"].should.contain(
-        "Things must be detached before deletion (arn: %s)" % cert_arn
+        f"Things must be detached before deletion (arn: {cert_arn})"
     )
     res = client.list_certificates()
     res.should.have.key("certificates").which.should.have.length_of(1)
@@ -215,7 +215,7 @@ def test_delete_certificate_validation():
     with pytest.raises(ClientError) as e:
         client.delete_certificate(certificateId=cert_id)
     e.value.response["Error"]["Message"].should.contain(
-        "Certificate policies must be detached before deletion (arn: %s)" % cert_arn
+        f"Certificate policies must be detached before deletion (arn: {cert_arn})"
     )
     res = client.list_certificates()
     res.should.have.key("certificates").which.should.have.length_of(1)

tests/test_iot/test_iot_policies.py

@@ -208,7 +208,7 @@ def test_policy_versions(iot_client):
         )
     err = exc.value.response["Error"]
     err["Message"].should.equal(
-        "The policy %s already has the maximum number of versions (5)" % policy_name
+        f"The policy {policy_name} already has the maximum number of versions (5)"
     )
 
     iot_client.delete_policy_version(policyName=policy_name, policyVersionId="1")

tests/test_iot/test_server.py

@@ -44,7 +44,7 @@ def test_list_attached_policies(url_encode_arn):
     if url_encode_arn:
         certificate_arn = quote(certificate_arn, safe="")
 
-    result = test_client.post("/attached-policies/{}".format(certificate_arn))
+    result = test_client.post(f"/attached-policies/{certificate_arn}")
     result.status_code.should.equal(200)
     result_dict = json.loads(result.data.decode("utf-8"))
     result_dict["policies"][0]["policyName"].should.equal("my-policy")

tests/test_iotdata/test_server.py

@@ -18,7 +18,7 @@ def test_iotdata_list():
 
     # just making sure that server is up
     thing_name = "nothing"
-    res = test_client.get("/things/{}/shadow".format(thing_name))
+    res = test_client.get(f"/things/{thing_name}/shadow")
     res.status_code.should.equal(404)
 
 
@@ -37,5 +37,5 @@ def test_publish(url_encode_topic):
     topic = "test/topic"
     topic_for_path = quote(topic, safe="") if url_encode_topic else topic
 
-    result = test_client.post("/topics/{}".format(topic_for_path))
+    result = test_client.post(f"/topics/{topic_for_path}")
     result.status_code.should.equal(200)

tests/test_kinesis/test_kinesis.py

@@ -97,7 +97,7 @@ def test_list_many_streams():
     conn = boto3.client("kinesis", region_name="us-west-2")
 
     for i in range(11):
-        conn.create_stream(StreamName="stream%d" % i, ShardCount=1)
+        conn.create_stream(StreamName=f"stream{i}", ShardCount=1)
 
     resp = conn.list_streams()
     stream_names = resp["StreamNames"]
@@ -124,7 +124,7 @@ def test_describe_stream_summary():
     stream["StreamName"].should.equal(stream_name)
     stream["OpenShardCount"].should.equal(shard_count)
     stream["StreamARN"].should.equal(
-        "arn:aws:kinesis:us-west-2:{}:stream/{}".format(ACCOUNT_ID, stream_name)
+        f"arn:aws:kinesis:us-west-2:{ACCOUNT_ID}:stream/{stream_name}"
     )
     stream["StreamStatus"].should.equal("ACTIVE")
 

tests/test_kinesisvideoarchivedmedia/test_kinesisvideoarchivedmedia.py

@@ -23,9 +23,7 @@ def test_get_hls_streaming_session_url():
         endpoint_url=data_endpoint,
     )
     res = client.get_hls_streaming_session_url(StreamName=stream_name)
-    reg_exp = r"^{}/hls/v1/getHLSMasterPlaylist.m3u8\?SessionToken\=.+$".format(
+    reg_exp = rf"^{data_endpoint}/hls/v1/getHLSMasterPlaylist.m3u8\?SessionToken\=.+$"
-        data_endpoint
-    )
     res.should.have.key("HLSStreamingSessionURL").which.should.match(reg_exp)
 
 
@@ -47,9 +45,7 @@ def test_get_dash_streaming_session_url():
         endpoint_url=data_endpoint,
     )
     res = client.get_dash_streaming_session_url(StreamName=stream_name)
-    reg_exp = r"^{}/dash/v1/getDASHManifest.mpd\?SessionToken\=.+$".format(
+    reg_exp = rf"^{data_endpoint}/dash/v1/getDASHManifest.mpd\?SessionToken\=.+$"
-        data_endpoint
-    )
     res.should.have.key("DASHStreamingSessionURL").which.should.match(reg_exp)
 
 

tests/test_kms/test_kms_boto3.py

@@ -65,9 +65,7 @@ def test_create_key():
     )
 
     key["KeyMetadata"]["Arn"].should.equal(
-        "arn:aws:kms:us-east-1:{}:key/{}".format(
+        f"arn:aws:kms:us-east-1:{ACCOUNT_ID}:key/{key['KeyMetadata']['KeyId']}"
-            ACCOUNT_ID, key["KeyMetadata"]["KeyId"]
-        )
     )
     key["KeyMetadata"]["AWSAccountId"].should.equal(ACCOUNT_ID)
     key["KeyMetadata"]["CreationDate"].should.be.a(datetime)
@@ -262,7 +260,7 @@ def test__create_alias__can_create_multiple_aliases_for_same_key_id():
     aliases = client.list_aliases(KeyId=key_id)["Aliases"]
 
     for name in alias_names:
-        alias_arn = "arn:aws:kms:us-east-1:{}:{}".format(ACCOUNT_ID, name)
+        alias_arn = f"arn:aws:kms:us-east-1:{ACCOUNT_ID}:{name}"
         aliases.should.contain(
             {"AliasName": name, "AliasArn": alias_arn, "TargetKeyId": key_id}
         )
@@ -278,8 +276,8 @@ def test_list_aliases():
     aliases.should.have.length_of(14)
     default_alias_names = ["aws/ebs", "aws/s3", "aws/redshift", "aws/rds"]
     for name in default_alias_names:
-        full_name = "alias/{}".format(name)
+        full_name = f"alias/{name}"
-        arn = "arn:aws:kms:{}:{}:{}".format(region, ACCOUNT_ID, full_name)
+        arn = f"arn:aws:kms:{region}:{ACCOUNT_ID}:{full_name}"
         aliases.should.contain({"AliasName": full_name, "AliasArn": arn})
 
 
@@ -991,9 +989,7 @@ def test__create_alias__raises_if_alias_has_restricted_characters(name):
     err = ex.value.response["Error"]
     err["Code"].should.equal("ValidationException")
     err["Message"].should.equal(
-        "1 validation error detected: Value '{}' at 'aliasName' failed to satisfy constraint: Member must satisfy regular expression pattern: ^[a-zA-Z0-9:/_-]+$".format(
+        f"1 validation error detected: Value '{name}' at 'aliasName' failed to satisfy constraint: Member must satisfy regular expression pattern: ^[a-zA-Z0-9:/_-]+$"
-            name
-        )
     )
 
 

tests/test_logs/test_integration.py

@@ -158,9 +158,9 @@ def test_put_subscription_filter_with_lambda():
     msg_showed_up, received_message = _wait_for_log_msg(
         client_logs, "/aws/lambda/test", "awslogs"
     )
-    assert msg_showed_up, "CloudWatch log event was not found. All logs: {}".format(
+    assert (
-        received_message
+        msg_showed_up
-    )
+    ), f"CloudWatch log event was not found. All logs: {received_message}"
 
     data = json.loads(received_message)["awslogs"]["data"]
     response = json.loads(
@@ -229,9 +229,9 @@ def test_subscription_filter_applies_to_new_streams():
     msg_showed_up, received_message = _wait_for_log_msg(
         client_logs, "/aws/lambda/test", "awslogs"
     )
-    assert msg_showed_up, "CloudWatch log event was not found. All logs: {}".format(
+    assert (
-        received_message
+        msg_showed_up
-    )
+    ), f"CloudWatch log event was not found. All logs: {received_message}"
 
     data = json.loads(received_message)["awslogs"]["data"]
     response = json.loads(

tests/test_logs/test_logs.py

@@ -1087,7 +1087,7 @@ def test_describe_log_streams_paging():
     resp["logStreams"].should.have.length_of(2)
     resp["logStreams"][0]["arn"].should.contain(log_group_name)
     resp["nextToken"].should.equal(
-        "{}@{}".format(log_group_name, resp["logStreams"][1]["logStreamName"])
+        f"{log_group_name}@{resp['logStreams'][1]['logStreamName']}"
     )
 
     resp = client.describe_log_streams(
@@ -1096,7 +1096,7 @@ def test_describe_log_streams_paging():
     resp["logStreams"].should.have.length_of(1)
     resp["logStreams"][0]["arn"].should.contain(log_group_name)
     resp["nextToken"].should.equal(
-        "{}@{}".format(log_group_name, resp["logStreams"][0]["logStreamName"])
+        f"{log_group_name}@{resp['logStreams'][0]['logStreamName']}"
     )
 
     resp = client.describe_log_streams(
@@ -1170,7 +1170,7 @@ def test_get_too_many_log_events(nr_of_events):
     err["Code"].should.equal("InvalidParameterException")
     err["Message"].should.contain("1 validation error detected")
     err["Message"].should.contain(
-        "Value '{}' at 'limit' failed to satisfy constraint".format(nr_of_events)
+        f"Value '{nr_of_events}' at 'limit' failed to satisfy constraint"
     )
     err["Message"].should.contain("Member must have value less than or equal to 10000")
 
@@ -1194,7 +1194,7 @@ def test_filter_too_many_log_events(nr_of_events):
     err["Code"].should.equal("InvalidParameterException")
     err["Message"].should.contain("1 validation error detected")
     err["Message"].should.contain(
-        "Value '{}' at 'limit' failed to satisfy constraint".format(nr_of_events)
+        f"Value '{nr_of_events}' at 'limit' failed to satisfy constraint"
     )
     err["Message"].should.contain("Member must have value less than or equal to 10000")
 
@@ -1209,7 +1209,7 @@ def test_describe_too_many_log_groups(nr_of_groups):
     err["Code"].should.equal("InvalidParameterException")
     err["Message"].should.contain("1 validation error detected")
     err["Message"].should.contain(
-        "Value '{}' at 'limit' failed to satisfy constraint".format(nr_of_groups)
+        f"Value '{nr_of_groups}' at 'limit' failed to satisfy constraint"
     )
     err["Message"].should.contain("Member must have value less than or equal to 50")
 
@@ -1226,7 +1226,7 @@ def test_describe_too_many_log_streams(nr_of_streams):
     err["Code"].should.equal("InvalidParameterException")
     err["Message"].should.contain("1 validation error detected")
     err["Message"].should.contain(
-        "Value '{}' at 'limit' failed to satisfy constraint".format(nr_of_streams)
+        f"Value '{nr_of_streams}' at 'limit' failed to satisfy constraint"
     )
     err["Message"].should.contain("Member must have value less than or equal to 50")
 
@@ -1242,9 +1242,7 @@ def test_create_log_group_invalid_name_length(length):
     err["Code"].should.equal("InvalidParameterException")
     err["Message"].should.contain("1 validation error detected")
     err["Message"].should.contain(
-        "Value '{}' at 'logGroupName' failed to satisfy constraint".format(
+        f"Value '{log_group_name}' at 'logGroupName' failed to satisfy constraint"
-            log_group_name
-        )
     )
     err["Message"].should.contain("Member must have length less than or equal to 512")
 
@@ -1263,7 +1261,7 @@ def test_describe_log_streams_invalid_order_by(invalid_orderby):
     err["Code"].should.equal("InvalidParameterException")
     err["Message"].should.contain("1 validation error detected")
     err["Message"].should.contain(
-        "Value '{}' at 'orderBy' failed to satisfy constraint".format(invalid_orderby)
+        f"Value '{invalid_orderby}' at 'orderBy' failed to satisfy constraint"
     )
     err["Message"].should.contain(
         "Member must satisfy enum value set: [LogStreamName, LastEventTime]"

tests/test_logs/test_logs_filter.py

@@ -82,9 +82,7 @@ class TestLogFilterParameters(TestLogFilter):
         timestamp = int(unix_time_millis(datetime.utcnow()))
         messages = []
         for i in range(25):
-            messages.append(
+            messages.append({"message": f"Message number {i}", "timestamp": timestamp})
-                {"message": "Message number {}".format(i), "timestamp": timestamp}
-            )
             timestamp += 100
 
         self.conn.put_log_events(

tests/test_managedblockchain/test_managedblockchain_members.py

@@ -171,7 +171,7 @@ def test_create_another_member_withopts():
         )
     err = ex.value.response["Error"]
     err["Code"].should.equal("InvalidRequestException")
-    err["Message"].should.contain("Invitation {0} not valid".format(invitation_id))
+    err["Message"].should.contain(f"Invitation {invitation_id} not valid")
 
     # Delete member 2
     conn.delete_member(NetworkId=network_id, MemberId=member_id2)
@@ -186,7 +186,7 @@ def test_create_another_member_withopts():
         conn.get_member(NetworkId=network_id, MemberId=member_id2)
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceNotFoundException")
-    err["Message"].should.contain("Member {0} not found".format(member_id2))
+    err["Message"].should.contain(f"Member {member_id2} not found")
 
     # Delete member 1
     conn.delete_member(NetworkId=network_id, MemberId=member_id)
@@ -422,9 +422,7 @@ def test_create_another_member_alreadyhave():
     err = ex.value.response["Error"]
     err["Code"].should.equal("InvalidRequestException")
     err["Message"].should.contain(
-        "Member name {0} already exists in network {1}".format(
+        f"Member name testmember1 already exists in network {network_id}"
-            "testmember1", network_id
-        )
     )
 
 

tests/test_managedblockchain/test_managedblockchain_nodes.py

@@ -78,7 +78,7 @@ def test_create_node():
         conn.get_node(NetworkId=network_id, MemberId=member_id, NodeId=node_id)
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceNotFoundException")
-    err["Message"].should.contain("Node {0} not found".format(node_id))
+    err["Message"].should.contain(f"Node {node_id} not found")
 
 
 @mock_managedblockchain
@@ -147,7 +147,7 @@ def test_create_node_standard_edition():
         conn.list_nodes(NetworkId=network_id, MemberId=member_id)
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceNotFoundException")
-    err["Message"].should.contain("Member {0} not found".format(member_id))
+    err["Message"].should.contain(f"Member {member_id} not found")
 
 
 @mock_managedblockchain
@@ -196,7 +196,7 @@ def test_create_too_many_nodes():
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceLimitExceededException")
     err["Message"].should.contain(
-        "Maximum number of nodes exceeded in member {0}".format(member_id)
+        f"Maximum number of nodes exceeded in member {member_id}"
     )
 
 

tests/test_managedblockchain/test_managedblockchain_proposalvotes.py

@@ -313,7 +313,7 @@ def test_vote_on_proposal_expiredproposal():
         err = ex.value.response["Error"]
         err["Code"].should.equal("InvalidRequestException")
         err["Message"].should.contain(
-            "Proposal {0} is expired and you cannot vote on it.".format(proposal_id)
+            f"Proposal {proposal_id} is expired and you cannot vote on it."
         )
 
         # Get proposal details - should be EXPIRED
@@ -633,7 +633,7 @@ def test_vote_on_proposal_alreadyvoted():
     err = ex.value.response["Error"]
     err["Code"].should.equal("ResourceAlreadyExistsException")
     err["Message"].should.contain(
-        "Member {0} has already voted on proposal {1}.".format(member_id, proposal_id)
+        f"Member {member_id} has already voted on proposal {proposal_id}."
     )
 
 

tests/test_medialive/test_medialive.py

@@ -11,7 +11,7 @@ region = "eu-west-1"
 def _create_input_config(name, **kwargs):
     role_arn = kwargs.get(
         "role_arn",
-        "arn:aws:iam::{}:role/TestMediaLiveInputCreateRole".format(ACCOUNT_ID),
+        f"arn:aws:iam::{ACCOUNT_ID}:role/TestMediaLiveInputCreateRole",
     )
     input_type = kwargs.get("type", "RTP_PUSH")
     request_id = kwargs.get("request_id", uuid4().hex)
@@ -52,7 +52,7 @@ def _create_input_config(name, **kwargs):
 def _create_channel_config(name, **kwargs):
     role_arn = kwargs.get(
         "role_arn",
-        "arn:aws:iam::{}:role/TestMediaLiveChannelCreateRole".format(ACCOUNT_ID),
+        f"arn:aws:iam::{ACCOUNT_ID}:role/TestMediaLiveChannelCreateRole",
     )
     input_id = kwargs.get("input_id", "an-attachment-id")
     input_settings = kwargs.get(
@@ -114,7 +114,7 @@ def test_create_channel_succeeds():
 
     response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
     response["Channel"]["Arn"].should.equal(
-        "arn:aws:medialive:channel:{}".format(response["Channel"]["Id"])
+        f"arn:aws:medialive:channel:{response['Channel']['Id']}"
     )
     response["Channel"]["Destinations"].should.equal(channel_config["Destinations"])
     response["Channel"]["EncoderSettings"].should.equal(
@@ -175,7 +175,7 @@ def test_describe_channel_succeeds():
     )
 
     describe_response["Arn"].should.equal(
-        "arn:aws:medialive:channel:{}".format(describe_response["Id"])
+        f"arn:aws:medialive:channel:{describe_response['Id']}"
     )
     describe_response["Destinations"].should.equal(channel_config["Destinations"])
     describe_response["EncoderSettings"].should.equal(channel_config["EncoderSettings"])
@@ -256,7 +256,7 @@ def test_create_input_succeeds():
     r_input = create_response["Input"]
     input_id = r_input["Id"]
     assert len(input_id) > 1
-    r_input["Arn"].should.equal("arn:aws:medialive:input:{}".format(r_input["Id"]))
+    r_input["Arn"].should.equal(f"arn:aws:medialive:input:{r_input['Id']}")
     r_input["Name"].should.equal(input_name)
     r_input["AttachedChannels"].should.equal([])
     r_input["Destinations"].should.equal(input_config["Destinations"])

tests/test_mediapackage/test_mediapackage.py

@@ -60,9 +60,7 @@ def test_create_channel_succeeds():
 
     response = client.create_channel(**channel_config)
     response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
-    response["Arn"].should.equal(
+    response["Arn"].should.equal(f"arn:aws:mediapackage:channel:{response['Id']}")
-        "arn:aws:mediapackage:channel:{}".format(response["Id"])
-    )
     response["Description"].should.equal("Awesome channel!")
     response["Id"].should.equal("channel-id")
     response["Tags"]["Customer"].should.equal("moto")
@@ -76,7 +74,7 @@ def test_describe_channel_succeeds():
     create_response = client.create_channel(**channel_config)
     describe_response = client.describe_channel(Id=create_response["Id"])
     describe_response["Arn"].should.equal(
-        "arn:aws:mediapackage:channel:{}".format(describe_response["Id"])
+        f"arn:aws:mediapackage:channel:{describe_response['Id']}"
     )
     describe_response["Description"].should.equal(channel_config["Description"])
     describe_response["Tags"]["Customer"].should.equal("moto")
@@ -90,7 +88,7 @@ def test_describe_unknown_channel_throws_error():
         client.describe_channel(Id=channel_id)
     err = err.value.response["Error"]
     err["Code"].should.equal("NotFoundException")
-    err["Message"].should.equal("channel with id={} not found".format(str(channel_id)))
+    err["Message"].should.equal(f"channel with id={channel_id} not found")
 
 
 @mock_mediapackage
@@ -101,7 +99,7 @@ def test_delete_unknown_channel_throws_error():
         client.delete_channel(Id=channel_id)
     err = err.value.response["Error"]
     err["Code"].should.equal("NotFoundException")
-    err["Message"].should.equal("channel with id={} not found".format(str(channel_id)))
+    err["Message"].should.equal(f"channel with id={channel_id} not found")
 
 
 @mock_mediapackage
@@ -131,7 +129,7 @@ def test_list_channels_succeds():
     len(channels_list).should.equal(1)
     first_channel = channels_list[0]
     first_channel["Arn"].should.equal(
-        "arn:aws:mediapackage:channel:{}".format(first_channel["Id"])
+        f"arn:aws:mediapackage:channel:{first_channel['Id']}"
     )
     first_channel["Description"].should.equal(channel_config["Description"])
     first_channel["Tags"]["Customer"].should.equal("moto")
@@ -145,7 +143,7 @@ def test_create_origin_endpoint_succeeds():
     response = client.create_origin_endpoint(**origin_endpoint_config)
     response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
     response["Arn"].should.equal(
-        "arn:aws:mediapackage:origin_endpoint:{}".format(response["Id"])
+        f"arn:aws:mediapackage:origin_endpoint:{response['Id']}"
     )
     response["ChannelId"].should.equal(origin_endpoint_config["ChannelId"])
     response["Description"].should.equal(origin_endpoint_config["Description"])
@@ -162,16 +160,14 @@ def test_describe_origin_endpoint_succeeds():
     describe_response = client.describe_origin_endpoint(Id=create_response["Id"])
     describe_response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
     describe_response["Arn"].should.equal(
-        "arn:aws:mediapackage:origin_endpoint:{}".format(describe_response["Id"])
+        f"arn:aws:mediapackage:origin_endpoint:{describe_response['Id']}"
     )
     describe_response["ChannelId"].should.equal(origin_endpoint_config["ChannelId"])
     describe_response["Description"].should.equal(origin_endpoint_config["Description"])
     describe_response["HlsPackage"].should.equal(origin_endpoint_config["HlsPackage"])
     describe_response["Origination"].should.equal("ALLOW")
     describe_response["Url"].should.equal(
-        "https://origin-endpoint.mediapackage.{}.amazonaws.com/{}".format(
+        f"https://origin-endpoint.mediapackage.{region}.amazonaws.com/{describe_response['Id']}"
-            region, describe_response["Id"]
-        )
     )
 
 
@@ -183,9 +179,7 @@ def test_describe_unknown_origin_endpoint_throws_error():
         client.describe_origin_endpoint(Id=channel_id)
     err = err.value.response["Error"]
     err["Code"].should.equal("NotFoundException")
-    err["Message"].should.equal(
+    err["Message"].should.equal(f"origin endpoint with id={channel_id} not found")
-        "origin endpoint with id={} not found".format(str(channel_id))
-    )
 
 
 @mock_mediapackage
@@ -213,9 +207,7 @@ def test_delete_unknown_origin_endpoint_throws_error():
         client.delete_origin_endpoint(Id=channel_id)
     err = err.value.response["Error"]
     err["Code"].should.equal("NotFoundException")
-    err["Message"].should.equal(
+    err["Message"].should.equal(f"origin endpoint with id={channel_id} not found")
-        "origin endpoint with id={} not found".format(str(channel_id))
-    )
 
 
 @mock_mediapackage
@@ -244,9 +236,7 @@ def test_update_unknown_origin_endpoint_throws_error():
         )
     err = err.value.response["Error"]
     err["Code"].should.equal("NotFoundException")
-    err["Message"].should.equal(
+    err["Message"].should.equal(f"origin endpoint with id={channel_id} not found")
-        "origin endpoint with id={} not found".format(str(channel_id))
-    )
 
 
 @mock_mediapackage
@@ -261,7 +251,7 @@ def test_list_origin_endpoint_succeeds():
     len(origin_endpoints_list).should.equal(1)
     first_origin_endpoint = origin_endpoints_list[0]
     first_origin_endpoint["Arn"].should.equal(
-        "arn:aws:mediapackage:origin_endpoint:{}".format(first_origin_endpoint["Id"])
+        f"arn:aws:mediapackage:origin_endpoint:{first_origin_endpoint['Id']}"
     )
     first_origin_endpoint["ChannelId"].should.equal(origin_endpoint_config["ChannelId"])
     first_origin_endpoint["Description"].should.equal(

tests/test_mediastore/test_mediastore.py

@@ -16,9 +16,7 @@ def test_create_container_succeeds():
     )
     container = response["Container"]
     response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
-    container["ARN"].should.equal(
+    container["ARN"].should.equal(f"arn:aws:mediastore:container:{container['Name']}")
-        "arn:aws:mediastore:container:{}".format(container["Name"])
-    )
     container["Name"].should.equal("Awesome container!")
     container["Status"].should.equal("CREATING")
 
@@ -33,9 +31,7 @@ def test_describe_container_succeeds():
     response = client.describe_container(ContainerName=container_name)
     response["ResponseMetadata"]["HTTPStatusCode"].should.equal(200)
     container = response["Container"]
-    container["ARN"].should.equal(
+    container["ARN"].should.equal(f"arn:aws:mediastore:container:{container_name}")
-        "arn:aws:mediastore:container:{}".format(container["Name"])
-    )
     container["Name"].should.equal("Awesome container!")
     container["Status"].should.equal("ACTIVE")
 

tests/test_opsworks/test_stack.py

@@ -22,7 +22,7 @@ def test_describe_stacks():
     client = boto3.client("opsworks", region_name="us-east-1")
     for i in range(1, 4):
         client.create_stack(
-            Name="test_stack_{0}".format(i),
+            Name=f"test_stack_{i}",
             Region="us-east-1",
             ServiceRoleArn="service_arn",
             DefaultInstanceProfileArn="profile_arn",

tests/test_organizations/test_organizations_boto3.py

@@ -1614,9 +1614,7 @@ def test_register_delegated_administrator():
     admin = response["DelegatedAdministrators"][0]
     admin["Id"].should.equal(account_id)
     admin["Arn"].should.equal(
-        "arn:aws:organizations::{0}:account/{1}/{2}".format(
+        f"arn:aws:organizations::{ACCOUNT_ID}:account/{org_id}/{account_id}"
-            ACCOUNT_ID, org_id, account_id
-        )
     )
     admin["Email"].should.equal(mockemail)
     admin["Name"].should.equal(mockname)
@@ -1740,9 +1738,7 @@ def test_list_delegated_administrators():
     admin = response["DelegatedAdministrators"][0]
     admin["Id"].should.equal(account_id_1)
     admin["Arn"].should.equal(
-        "arn:aws:organizations::{0}:account/{1}/{2}".format(
+        f"arn:aws:organizations::{ACCOUNT_ID}:account/{org_id}/{account_id_1}"
-            ACCOUNT_ID, org_id, account_id_1
-        )
     )
     admin["Email"].should.equal(mockemail)
     admin["Name"].should.equal(mockname)

tests/test_ram/test_ram.py

@@ -38,7 +38,7 @@ def test_create_resource_share():
         name="test",
         allowExternalPrincipals=False,
         resourceArns=[
-            "arn:aws:ec2:us-east-1:{}:transit-gateway/tgw-123456789".format(ACCOUNT_ID)
+            f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/tgw-123456789"
         ],
     )
 
@@ -80,7 +80,7 @@ def test_create_resource_share_errors():
     # when
     with pytest.raises(ClientError) as e:
         client.create_resource_share(
-            name="test", resourceArns=["arn:aws:iam::{}:role/test".format(ACCOUNT_ID)]
+            name="test", resourceArns=[f"arn:aws:iam::{ACCOUNT_ID}:role/test"]
         )
     ex = e.value
     ex.operation_name.should.equal("CreateResourceShare")
@@ -97,9 +97,7 @@ def test_create_resource_share_errors():
             name="test",
             principals=["invalid"],
             resourceArns=[
-                "arn:aws:ec2:us-east-1:{}:transit-gateway/tgw-123456789".format(
+                f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/tgw-123456789"
-                    ACCOUNT_ID
-                )
             ],
         )
     ex = e.value
@@ -129,7 +127,7 @@ def test_create_resource_share_with_organization():
         name="test",
         principals=[org_arn],
         resourceArns=[
-            "arn:aws:ec2:us-east-1:{}:transit-gateway/tgw-123456789".format(ACCOUNT_ID)
+            f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/tgw-123456789"
         ],
     )
 
@@ -142,7 +140,7 @@ def test_create_resource_share_with_organization():
         name="test",
         principals=[ou_arn],
         resourceArns=[
-            "arn:aws:ec2:us-east-1:{}:transit-gateway/tgw-123456789".format(ACCOUNT_ID)
+            f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/tgw-123456789"
         ],
     )
 
@@ -165,13 +163,9 @@ def test_create_resource_share_with_organization_errors():
     with pytest.raises(ClientError) as e:
         client.create_resource_share(
             name="test",
-            principals=[
+            principals=[f"arn:aws:organizations::{ACCOUNT_ID}:organization/o-unknown"],
-                "arn:aws:organizations::{}:organization/o-unknown".format(ACCOUNT_ID)
-            ],
             resourceArns=[
-                "arn:aws:ec2:us-east-1:{}:transit-gateway/tgw-123456789".format(
+                f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/tgw-123456789"
-                    ACCOUNT_ID
-                )
             ],
         )
     ex = e.value
@@ -187,13 +181,9 @@ def test_create_resource_share_with_organization_errors():
     with pytest.raises(ClientError) as e:
         client.create_resource_share(
             name="test",
-            principals=[
+            principals=[f"arn:aws:organizations::{ACCOUNT_ID}:ou/o-unknown/ou-unknown"],
-                "arn:aws:organizations::{}:ou/o-unknown/ou-unknown".format(ACCOUNT_ID)
-            ],
             resourceArns=[
-                "arn:aws:ec2:us-east-1:{}:transit-gateway/tgw-123456789".format(
+                f"arn:aws:ec2:us-east-1:{ACCOUNT_ID}:transit-gateway/tgw-123456789"
-                    ACCOUNT_ID
-                )
             ],
         )
     ex = e.value
@@ -284,9 +274,7 @@ def test_update_resource_share_errors():
     # when
     with pytest.raises(ClientError) as e:
         client.update_resource_share(
-            resourceShareArn="arn:aws:ram:us-east-1:{}:resource-share/not-existing".format(
+            resourceShareArn=f"arn:aws:ram:us-east-1:{ACCOUNT_ID}:resource-share/not-existing",
-                ACCOUNT_ID
-            ),
             name="test-update",
         )
     ex = e.value
@@ -294,9 +282,7 @@ def test_update_resource_share_errors():
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("UnknownResourceException")
     ex.response["Error"]["Message"].should.equal(
-        "ResourceShare arn:aws:ram:us-east-1:{}:resource-share/not-existing could not be found.".format(
+        f"ResourceShare arn:aws:ram:us-east-1:{ACCOUNT_ID}:resource-share/not-existing could not be found."
-            ACCOUNT_ID
-        )
     )
 
 
@@ -330,18 +316,14 @@ def test_delete_resource_share_errors():
     # when
     with pytest.raises(ClientError) as e:
         client.delete_resource_share(
-            resourceShareArn="arn:aws:ram:us-east-1:{}:resource-share/not-existing".format(
+            resourceShareArn=f"arn:aws:ram:us-east-1:{ACCOUNT_ID}:resource-share/not-existing"
-                ACCOUNT_ID
-            )
         )
     ex = e.value
     ex.operation_name.should.equal("DeleteResourceShare")
     ex.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
     ex.response["Error"]["Code"].should.contain("UnknownResourceException")
     ex.response["Error"]["Message"].should.equal(
-        "ResourceShare arn:aws:ram:us-east-1:{}:resource-share/not-existing could not be found.".format(
+        f"ResourceShare arn:aws:ram:us-east-1:{ACCOUNT_ID}:resource-share/not-existing could not be found."
-            ACCOUNT_ID
-        )
     )
 
 

tests/test_rds/test_filters.py

@@ -15,8 +15,8 @@ class TestDBInstanceFilters(object):
         cls.mock.start()
         client = boto3.client("rds", region_name="us-west-2")
         for i in range(10):
-            instance_identifier = "db-instance-{}".format(i)
+            instance_identifier = f"db-instance-{i}"
-            cluster_identifier = "db-cluster-{}".format(i)
+            cluster_identifier = f"db-cluster-{i}"
             engine = "postgres" if (i % 3) else "mysql"
             client.create_db_instance(
                 DBInstanceIdentifier=instance_identifier,
@@ -200,7 +200,7 @@ class TestDBSnapshotFilters(object):
         # We'll set up two instances (one postgres, one mysql)
         # with two snapshots each.
         for i in range(2):
-            identifier = "db-instance-{}".format(i)
+            identifier = f"db-instance-{i}"
             engine = "postgres" if i else "mysql"
             client.create_db_instance(
                 DBInstanceIdentifier=identifier,
@@ -210,7 +210,7 @@ class TestDBSnapshotFilters(object):
             for j in range(2):
                 client.create_db_snapshot(
                     DBInstanceIdentifier=identifier,
-                    DBSnapshotIdentifier="{}-snapshot-{}".format(identifier, j),
+                    DBSnapshotIdentifier=f"{identifier}-snapshot-{j}",
                 )
         cls.client = client