Cast to CaseInsensitiveDict

Author: adamtheturtle

tests/mock_vws/test_unexpected_json.py

@@ -7,6 +7,7 @@
 import pytest
 import requests
 from requests import codes
+from requests.structures import CaseInsensitiveDict
 
 from mock_vws._constants import ResultCodes
 from tests.mock_vws.utils import (
@@ -57,7 +58,7 @@ def test_does_not_take_data(
         }
 
         endpoint.prepared_request.body = content
-        endpoint.prepared_request.headers = headers
+        endpoint.prepared_request.headers = CaseInsensitiveDict(data=headers)
         endpoint.prepared_request.prepare_content_length(  # type: ignore
             body=content,
         )