Cleanup model ref resetting.

moto/core/models.py

@@ -466,10 +466,14 @@ def __new__(cls, *args, **kwargs):
 
 class BaseBackend(object):
 
-    def reset(self):
+    def _reset_model_refs(self):
+        # Remove all references to the models stored
         for service, models in model_data.items():
             for model_name, model in models.items():
                 model.instances = []
+
+    def reset(self):
+        self._reset_model_refs()
         self.__dict__ = {}
         self.__init__()
 

moto/sqs/models.py

@@ -379,6 +379,7 @@ def __init__(self, region_name):
 
     def reset(self):
         region_name = self.region_name
+        self._reset_model_refs()
         self.__dict__ = {}
         self.__init__(region_name)
 

tests/test_core/test_context_manager.py

@@ -2,7 +2,7 @@
 import boto3
 from moto import mock_sqs
 
-def test_reset_api():
+def test_context_manager_returns_mock():
     with mock_sqs() as sqs_mock:
         conn = boto3.client("sqs", region_name='us-west-1')
         conn.create_queue(QueueName="queue1")