@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"User-Agent": "testclient"}),
        ("/items", {"X-Header": "notvalid"}, 200, {"User-Agent": "testclient"}),
        ("/items", {"User-Agent": "FastAPI test"}, 200, {"User-Agent": "FastAPI test"}),
    ],
)
def test(path, headers, expected_status, expected_response, client: TestClient):

    out_path.parent.mkdir(parents=True, exist_ok=True)
    original_content = en_path.read_text(encoding="utf-8")
    old_translation: str | None = None
    if out_path.exists():
        print(f"Found existing translation: {out_path}")
        old_translation = out_path.read_text(encoding="utf-8")
    print(f"Translating {en_path} to {language} ({language_name})")
    agent = Agent("openai:gpt-5.2")

    prompt_segments = [

                        "x_tag": [],
                        "accept": "*/*",
                        "accept-encoding": "gzip, deflate",
                        "connection": "keep-alive",
                        "user-agent": "testclient",
                        "save-data": "true",
                        "if-modified-since": "yesterday",
                        "x-tag": ["one", "two"],
                    },
                }
            ]

                        "host": "testserver",
                        "accept": "*/*",
                        "accept-encoding": "gzip, deflate",
                        "connection": "keep-alive",
                        "user-agent": "testclient",
                    },
                }
            ]
        }
    )


def test_header_param_model_extra(client: TestClient):
    response = client.get(

    pass  # pragma: nocover


class Event(BaseModel):
    name: str
    total: float


events_callback_router = APIRouter()


@events_callback_router.get("{$callback_url}/events/{$request.body.title}")
def event_callback(event: Event):
    pass  # pragma: nocover


subrouter = APIRouter()


@subrouter.post("/invoices/", callbacks=invoices_callback_router.routes)

        `on_event` is deprecated, use `lifespan` event handlers instead.

        Read more about it in the
        [FastAPI docs for Lifespan Events](https://fastapi.tiangolo.com/advanced/events/#alternative-events-deprecated).
        """

        def decorator(func: DecoratedCallable) -> DecoratedCallable:
            self.add_event_handler(event_type, func)
            return func

    return {"result": result}
```

**Note**: This is the recommended way going forward, instead of using `startup` and `shutdown` events.

Read more about it in the new docs: [Advanced User Guide: Lifespan Events](https://fastapi.tiangolo.com/advanced/events/).

### Docs