ELB: describe_instance_health() should check LB existence (#5706)

moto/elb/exceptions.py

@@ -23,10 +23,17 @@ class CertificateNotFoundException(ELBClientError):
 
 
 class LoadBalancerNotFoundError(ELBClientError):
-    def __init__(self, cidr):
+    def __init__(self, name):
         super().__init__(
             "LoadBalancerNotFound",
-            f"The specified load balancer does not exist: {cidr}",
+            f"The specified load balancer does not exist: {name}",
+        )
+
+
+class NoActiveLoadBalancerFoundError(ELBClientError):
+    def __init__(self, name):
+        super().__init__(
+            "LoadBalancerNotFound", f"There is no ACTIVE Load Balancer named '{name}'"
         )
 
 

moto/elb/models.py

@@ -14,6 +14,7 @@ from .exceptions import (
     EmptyListenersError,
     InvalidSecurityGroupError,
     LoadBalancerNotFoundError,
+    NoActiveLoadBalancerFoundError,
     PolicyNotFoundError,
     TooManyTagsError,
     CertificateNotFoundException,
@@ -372,8 +373,11 @@ class ELBBackend(BaseBackend):
         return policies
 
     def describe_instance_health(self, lb_name, instances):
+        elb = self.get_load_balancer(lb_name)
+        if elb is None:
+            raise NoActiveLoadBalancerFoundError(name=lb_name)
         provided_ids = [i["InstanceId"] for i in instances]
-        registered_ids = self.get_load_balancer(lb_name).instance_ids
+        registered_ids = elb.instance_ids
         ec2_backend = ec2_backends[self.account_id][self.region_name]
         if len(provided_ids) == 0:
             provided_ids = registered_ids

tests/test_elb/test_elb.py

@@ -933,6 +933,17 @@ def test_describe_instance_health__with_instance_ids():
     instances_health[2]["State"].should.equal("OutOfService")
 
 
+@mock_elb
+def test_describe_instance_health_of_unknown_lb():
+    elb = boto3.client("elb", region_name="us-east-1")
+
+    with pytest.raises(ClientError) as exc:
+        elb.describe_instance_health(LoadBalancerName="what")
+    err = exc.value.response["Error"]
+    err["Code"].should.equal("LoadBalancerNotFound")
+    err["Message"].should.equal("There is no ACTIVE Load Balancer named 'what'")
+
+
 @mock_elb
 def test_add_remove_tags():
     client = boto3.client("elb", region_name="us-east-1")