def METHOD_NAME(
    self, clean_headers, add_request_headers, http_service, svc
):
    svc.get_url_details(url="http://example.com", headers={"X-Pre-Existing": 1})
    _args, kwargs = http_service.get.call_args
    clean_headers.assert_called_once_with({"X-Pre-Existing": 1})
    add_request_headers.assert_called_once_with(clean_headers.return_value)
    assert kwargs["headers"] == add_request_headers.return_value