tests: Refactor mock_http_conversation with deduplicating.

Move `get_response` inside of `mock_http_conversation`, as it is not
used anywhere else. Also create `assert_called_with_fields`.
`assert_called_with_fields` calls the `assert_called_with` method of a
mock object by using an HTTP request and a list of fields to look for.

zulip_bots/zulip_bots/test_lib.py

@@ -159,13 +159,6 @@ def read_bot_fixture_data(bot_name, test_name):
     http_data = json.loads(content)
     return http_data
 
-def get_response(http_response, http_headers):
-    # type: (Dict[str, Any], Dict[str, Any]) -> Any
-    mock_result = requests.Response()
-    mock_result._content = json.dumps(http_response).encode()  # type: ignore # This modifies a "hidden" attribute.
-    mock_result.status_code = http_headers.get('status', 200)
-    return mock_result
-
 @contextmanager
 def mock_http_conversation(http_data):
     # type: (Dict[str, Any]) -> Any
@@ -178,6 +171,31 @@ def mock_http_conversation(http_data):
     http_data should be fixtures data formatted like the data
     in zulip_bots/zulip_bots/bots/giphy/fixtures/test_normal.json
     """
+    def get_response(http_response, http_headers):
+        # type: (Dict[str, Any], Dict[str, Any]) -> Any
+        """Creates a fake `requests` Response with a desired HTTP response and
+        response headers.
+        """
+        mock_result = requests.Response()
+        mock_result._content = json.dumps(http_response).encode()  # type: ignore # This modifies a "hidden" attribute.
+        mock_result.status_code = http_headers.get('status', 200)
+        return mock_result
+
+    def assert_called_with_fields(mock_result, http_request, fields):
+        # type: (Any, Dict[str, Any], List[str]) -> None
+        """Calls `assert_called_with` on a mock object using an HTTP request.
+        Uses `fields` to determine which keys to look for in HTTP request and
+        to test; if a key is in `fields`, e.g., 'headers', it will be used in
+        the assertion.
+        """
+        args = {}
+
+        for field in fields:
+            if field in http_request:
+                args[field] = http_request[field]
+
+        mock_result.assert_called_with(http_request['api_url'], **args)
+
     http_request = http_data.get('request')
     http_response = http_data.get('response')
     http_headers = http_data.get('response-headers')
@@ -187,30 +205,20 @@ def mock_http_conversation(http_data):
         with patch('requests.get') as mock_get:
             mock_get.return_value = get_response(http_response, http_headers)
             yield
-            if 'params' in http_request:
+            assert_called_with_fields(
-                params = http_request.get('params', None)
+                mock_get,
-                mock_get.assert_called_with(http_request['api_url'], params=params)
+                http_request,
-            elif 'headers' in http_request:
+                ['params', 'headers']
-                headers = http_request.get('headers', None)
+            )
-                mock_get.assert_called_with(http_request['api_url'], headers=headers)
-            else:
-                mock_get.assert_called_with(http_request['api_url'])
     else:
         with patch('requests.post') as mock_post:
             mock_post.return_value = get_response(http_response, http_headers)
             yield
-            if 'json' in http_request:
+            assert_called_with_fields(
-                json = http_request.get('json', None)
+                mock_post,
-                if 'params' in http_request:
+                http_request,
-                    params = http_request.get('params', None)
+                ['params', 'headers', 'json']
-                    mock_post.assert_called_with(http_request['api_url'], json=json, params=params)
+            )
-                else:
-                    mock_post.assert_called_with(http_request['api_url'], json=json)
-            elif 'params' in http_request:
-                params = http_request.get('params', None)
-                mock_post.assert_called_with(http_request['api_url'], params=params)
-            else:
-                mock_post.assert_called_with(http_request['api_url'])
 
 class BotTestCase(StubBotTestCase):
     """Test class for common Bot test helper methods"""