Core responses: Add missing registered() (#6597)

moto/core/responses_custom_registry.py

@@ -17,6 +17,13 @@ class CustomRegistry(responses.registries.FirstMatchRegistry):
     def __init__(self) -> None:
         self._registered: Dict[str, List[responses.BaseResponse]] = defaultdict(list)
 
+    @property
+    def registered(self) -> List[responses.BaseResponse]:
+        res = []
+        for resps in self._registered.values():
+            res += resps
+        return res
+
     def add(self, response: responses.BaseResponse) -> responses.BaseResponse:
         if response not in self._registered[response.method]:
             self._registered[response.method].append(response)

tests/test_apigateway/test_apigateway_integration.py

@@ -15,7 +15,8 @@ def test_http_integration():
     responses_mock.add(
         responses_mock.GET, "http://httpbin.org/robots.txt", body="a fake response"
     )
-
+    registered = responses_mock.registered()
+    assert isinstance(registered, list) and len(registered) > 1
     region_name = "us-west-2"
     client = boto3.client("apigateway", region_name=region_name)
     response = client.create_rest_api(name="my_api", description="this is my api")