assert not override4 or "x-level4" in response.headers
    assert not override5 or "x-level5" in response.headers


def test_openapi():
    client = TestClient(app)
    with warnings.catch_warnings(record=True) as w:
        warnings.simplefilter("always")
        response = client.get("/openapi.json")
        assert issubclass(w[-1].category, UserWarning)

    * **Talks**:
        * [PyConBY 2020: Serve ML models easily with FastAPI](https://www.youtube.com/watch?v=z9K5pwb0rt8) by [Sebastián Ramírez (tiangolo)](https://twitter.com/tiangolo).
        * [[VIRTUAL] Py.Amsterdam's flying Software Circus: Intro to FastAPI](https://www.youtube.com/watch?v=PnpTY1f4k2U) by [Sebastián Ramírez (tiangolo)](https://twitter.com/tiangolo).