diff --git a/zulip_bots/zulip_bots/bots/trello/fixtures/invalid_key.json b/zulip_bots/zulip_bots/bots/trello/fixtures/invalid_key.json
new file mode 100644
index 0000000..ae06ce3
--- /dev/null
+++ b/zulip_bots/zulip_bots/bots/trello/fixtures/invalid_key.json
@@ -0,0 +1,15 @@
+{
+  "meta": {
+    "is_raw_response": true
+  },
+  "request": {
+    "api_url": "https://api.trello.com/1/members/TEST/",
+    "params": {
+        "key": "TEST",
+        "token": "TEST"
+    }
+  },
+  "response": "invalid key",
+  "response-headers": {
+  }
+}
diff --git a/zulip_bots/zulip_bots/bots/trello/test_trello.py b/zulip_bots/zulip_bots/bots/trello/test_trello.py
index b54656e..3df36cf 100644
--- a/zulip_bots/zulip_bots/bots/trello/test_trello.py
+++ b/zulip_bots/zulip_bots/bots/trello/test_trello.py
@@ -27,7 +27,8 @@ class TestTrelloBot(BotTestCase):
 
     def test_bot_quit_with_invalid_config(self) -> None:
         with self.mock_config_info(mock_config), self.assertRaises(StubBotHandler.BotQuitException):
-            TrelloHandler().initialize(StubBotHandler())
+            with self.mock_http_conversation('invalid_key'):
+                TrelloHandler().initialize(StubBotHandler())
 
     def test_invalid_command(self) -> None:
         with self.mock_config_info(mock_config), patch('requests.get'):
diff --git a/zulip_bots/zulip_bots/request_test_lib.py b/zulip_bots/zulip_bots/request_test_lib.py
index e8651f1..9eb9cee 100644
--- a/zulip_bots/zulip_bots/request_test_lib.py
+++ b/zulip_bots/zulip_bots/request_test_lib.py
@@ -18,18 +18,21 @@ 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
+    def get_response(http_response, http_headers, is_raw_response):
+        # type: (Dict[str, Any], Dict[str, Any], bool) -> 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.
+        if is_raw_response:
+            mock_result._content = http_response.encode()  # type: ignore # This modifies a "hidden" attribute.
+        else:
+            mock_result._content = json.dumps(http_response).encode()  # type: ignore # See above.
         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
+    def assert_called_with_fields(mock_result, http_request, fields, meta):
+        # type: (Any, Dict[str, Any], List[str], Dict[str, Any]) -> 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
@@ -51,34 +54,40 @@ def mock_http_conversation(http_data):
         print("ERROR: Failed to find 'request', 'response' or 'response-headers' fields in fixture")
         raise
 
+    meta = http_data.get('meta', dict())
+    is_raw_response = meta.get('is_raw_response', False)
+
     http_method = http_request.get('method', 'GET')
 
     if http_method == 'GET':
         with patch('requests.get') as mock_get:
-            mock_get.return_value = get_response(http_response, http_headers)
+            mock_get.return_value = get_response(http_response, http_headers, is_raw_response)
             yield
             assert_called_with_fields(
                 mock_get,
                 http_request,
-                ['params', 'headers']
+                ['params', 'headers'],
+                meta
             )
     elif http_method == 'PATCH':
         with patch('requests.patch') as mock_patch:
-            mock_patch.return_value = get_response(http_response, http_headers)
+            mock_patch.return_value = get_response(http_response, http_headers, is_raw_response)
             yield
             assert_called_with_fields(
                 mock_patch,
                 http_request,
-                ['params', 'headers', 'json', 'data']
+                ['params', 'headers', 'json', 'data'],
+                meta
             )
     else:
         with patch('requests.post') as mock_post:
-            mock_post.return_value = get_response(http_response, http_headers)
+            mock_post.return_value = get_response(http_response, http_headers, is_raw_response)
             yield
             assert_called_with_fields(
                 mock_post,
                 http_request,
-                ['params', 'headers', 'json', 'data']
+                ['params', 'headers', 'json', 'data'],
+                meta
             )
 
 @contextmanager