!!! tip "Tipp"
    Wenn Sie den Code zum Dokumentieren eines Callbacks schreiben, kann es hilfreich sein, sich vorzustellen, dass Sie dieser *externe Entwickler* sind. Und dass Sie derzeit die *externe API* implementieren, nicht *Ihre API*.

```

Whenever you need the client to pass information in the request and you don't know how to, you can search (Google) how to do it in `httpx`, or even how to do it with `requests`, as HTTPX's design is based on Requests' design.

Then you just do the same in your tests.

E.g.:

* To pass a *path* or *query* parameter, add it to the URL itself.
* To pass a JSON body, pass a Python object (e.g. a `dict`) to the parameter `json`.

@app.get(
    "/a",
    response_class=JsonApiResponse,
    responses={500: {"description": "Error", "model": JsonApiError}},
)
async def a():
    pass  # pragma: no cover


@app.get("/b", responses={500: {"description": "Error", "model": Error}})
async def b():
    pass  # pragma: no cover


client = TestClient(app)


def test_openapi_schema():
    response = client.get("/openapi.json")

@app.get(
    "/a",
    status_code=204,
    response_class=JsonApiResponse,
    responses={500: {"description": "Error", "model": JsonApiError}},
)
async def a():
    pass


@app.get("/b", responses={204: {"description": "No Content"}})
async def b():
    pass  # pragma: no cover


client = TestClient(app)


def test_get_response():
    response = client.get("/a")
    assert response.status_code == 204, response.text

@callback_router.get(
    "{$callback_url}/callback/", responses={400: {"model": CustomModel}}
)
def callback_route():
    pass  # pragma: no cover


@app.post("/", callbacks=callback_router.routes)
def main_route(callback_url: HttpUrl):
    pass  # pragma: no cover


client = TestClient(app)


def test_openapi_schema():
    response = client.get("/openapi.json")

    ```Python hl_lines="22"
    {!> ../../../docs_src/dependencies/tutorial005.py!}
    ```

!!! info
    Beachten Sie, dass wir in der *Pfadoperation-Funktion* nur eine einzige Abhängigkeit deklarieren, den `query_or_cookie_extractor`.

    Aber **FastAPI** wird wissen, dass es zuerst `query_extractor` auflösen muss, um dessen Resultat `query_or_cookie_extractor` zu übergeben, wenn dieses aufgerufen wird.

```mermaid

@app.post("/products")
async def create_product(data: Product = Body(media_type=media_type, embed=True)):
    pass  # pragma: no cover


@app.post("/shops")
async def create_shop(
    data: Shop = Body(media_type=media_type),
    included: typing.List[Product] = Body(default=[], media_type=media_type),
):
    pass  # pragma: no cover


client = TestClient(app)


def test_openapi_schema():

class FooBaseModel(BaseModel):
    if PYDANTIC_V2:
        model_config = ConfigDict(extra="forbid")
    else:

        class Config:
            extra = "forbid"


class Foo(FooBaseModel):
    pass


app = FastAPI()


@app.post("/")
async def post(
    foo: Union[Foo, None] = None,
):
    return foo


client = TestClient(app)


def test_call_invalid():

* **Uvicorn**:
    * Bietet die beste Leistung, da außer dem Server selbst nicht viel zusätzlicher Code vorhanden ist.

The middleware function receives:

* The `request`.
* A function `call_next` that will receive the `request` as a parameter.
    * This function will pass the `request` to the corresponding *path operation*.
    * Then it returns the `response` generated by the corresponding *path operation*.
* You can then modify further the `response` before returning it.