@app.get("/")
        def read_root() -> Union[Response, None]:
            return Response(content="Foo")  # pragma: no cover

    assert "valid Pydantic field type" in e.value.args[0]
    assert "parameter response_model=None" in e.value.args[0]


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {

                        )
                        if current_status_code is not None:
                            response_args["status_code"] = current_status_code
                        if sub_response.status_code:
                            response_args["status_code"] = sub_response.status_code
                        content = await serialize_response(
                            field=response_field,