Delete event rule when deleted from cloudformation template (#4382)

moto/events/models.py

@@ -271,6 +271,13 @@ class Rule(CloudFormationModel):
             new_resource_name, cloudformation_json, region_name
         )
 
+    @classmethod
+    def delete_from_cloudformation_json(
+        cls, resource_name, cloudformation_json, region_name
+    ):
+        event_backend = events_backends[region_name]
+        event_backend.delete_rule(resource_name)
+
     def describe(self):
         attributes = {
             "Arn": self.arn,

tests/test_events/test_events_cloudformation.py

@@ -1,8 +1,10 @@
+import pytest
 import copy
 from string import Template
 
 import boto3
 import json
+from botocore.exceptions import ClientError
 from moto import mock_cloudformation, mock_events
 import sure  # noqa
 
@@ -60,6 +62,15 @@ rule_template = Template(
 )
 
 
+empty = json.dumps(
+    {
+        "AWSTemplateFormatVersion": "2010-09-09",
+        "Description": "EventBridge Rule Test",
+        "Resources": {},
+    }
+)
+
+
 @mock_events
 @mock_cloudformation
 def test_create_archive():
@@ -154,3 +165,24 @@ def test_create_rule():
 
     response["Arn"].should.equal(rule_arn)
     response["EventPattern"].should.equal('{"detail-type": ["SomeDetailType"]}')
+
+
+@mock_events
+@mock_cloudformation
+def test_delete_rule():
+    # given
+    cfn_client = boto3.client("cloudformation", region_name="eu-central-1")
+    name = "test-rule"
+    stack_name = "test-stack"
+    template = rule_template.substitute({"rule_name": name})
+    cfn_client.create_stack(StackName=stack_name, TemplateBody=template)
+
+    # when
+    cfn_client.update_stack(StackName=stack_name, TemplateBody=empty)
+
+    # then
+    events_client = boto3.client("events", region_name="eu-central-1")
+
+    with pytest.raises(ClientError, match="does not exist") as e:
+
+        events_client.describe_rule(Name=name)