client = TestClient(app)


def test_endpoint_works():
    response = client.post("/", json=[1, 2, 3])
    assert response.json() == 6


def test_exception_handler_body_access():
    response = client.post("/", json={"numbers": [1, 2, 3]})
    assert response.json() == IsDict(
        {
            "detail": {
                "errors": [
                    {

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Can raise exceptions, including HTTPException
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise Exception
        dep -->> handler: Raise Exception

- ✅ Tests with [Pytest](https://pytest.org).
- 📞 [Traefik](https://traefik.io) as a reverse proxy / load balancer.
- 🚢 Deployment instructions using Docker Compose, including how to set up a frontend Traefik proxy to handle automatic HTTPS certificates.

    * Numbers (`int`, `float`) with min and max values, etc.

* Validation for more exotic types, like:
    * URL.
    * Email.
    * UUID.
    * ...and others.

All the validation is handled by the well-established and robust **Pydantic**.

### Security and authentication

Security and authentication integrated. Without any compromise with databases or data models.

    )


async def request_validation_exception_handler(
    request: Request, exc: RequestValidationError
) -> JSONResponse:
    return JSONResponse(
        status_code=HTTP_422_UNPROCESSABLE_ENTITY,
        content={"detail": jsonable_encoder(exc.errors())},
    )


async def websocket_request_validation_exception_handler(
    websocket: WebSocket, exc: WebSocketRequestValidationError
) -> None:

Sie könnten einen benutzerdefinierten Exceptionhandler mittels `@app.exception_handler()` hinzufügen:

```Python hl_lines="5-7  13-18  24"
{!../../../docs_src/handling_errors/tutorial003.py!}
```

Wenn Sie nun `/unicorns/yolo` anfragen, `raise`d die *Pfadoperation* eine `UnicornException`.

Aber diese wird von `unicorn_exception_handler` gehandhabt.

      advanced/conditional-openapi.md: how-to/conditional-openapi.md
      advanced/extending-openapi.md: how-to/extending-openapi.md
  mkdocstrings:
    handlers:
      python:
        options:
          extensions:
          - griffe_typingdoc
          show_root_heading: true
          show_if_no_docstring: true
          preload_modules:
          - httpx

        )
        self.exception_handlers: Dict[
            Any, Callable[[Request, Any], Union[Response, Awaitable[Response]]]
        ] = {} if exception_handlers is None else dict(exception_handlers)
        self.exception_handlers.setdefault(HTTPException, http_exception_handler)
        self.exception_handlers.setdefault(
            RequestValidationError, request_validation_exception_handler
        )

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

    opt raise
        dep -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        dep -->> dep: Raise other exception
    end
    dep ->> operation: Run dependency, e.g. DB session
    opt raise
        operation -->> dep: Raise HTTPException
        dep -->> handler: Auto forward exception
        handler -->> client: HTTP error response