# Testing Events: startup - shutdown

When you need your event handlers (`startup` and `shutdown`) to run in your tests, you can use the `TestClient` with a `with` statement:

```Python hl_lines="9-12  20-24"
{!../../../docs_src/app_testing/tutorial003.py!}

from fastapi import FastAPI, HTTPException
from fastapi.exception_handlers import (
    http_exception_handler,
    request_validation_exception_handler,
)
from fastapi.exceptions import RequestValidationError
from starlette.exceptions import HTTPException as StarletteHTTPException

app = FastAPI()


@app.exception_handler(StarletteHTTPException)
async def custom_http_exception_handler(request, exc):
    print(f"OMG! An HTTP error!: {repr(exc)}")

new_app = UnicornMiddleware(app, some_config="rainbow")
```

But FastAPI (actually Starlette) provides a simpler way to do it that makes sure that the internal middlewares to handle server errors and custom exception handlers work properly.

For that, you use `app.add_middleware()` (as in the example for CORS).

```Python
from fastapi import FastAPI
from unicorn import UnicornMiddleware

app = FastAPI()

```Python
from starlette.exceptions import HTTPException as StarletteHTTPException

```

### 复用 **FastAPI** 异常处理器

FastAPI 支持先对异常进行某些处理，然后再使用 **FastAPI** 中处理该异常的默认异常处理器。

从 `fastapi.exception_handlers` 中导入要复用的默认异常处理器：

```Python hl_lines="2-5  15  21"
{!../../../docs_src/handling_errors/tutorial006.py!}

```

虽然，本例只是输出了夸大其词的错误信息。

from starlette.exceptions import HTTPException as StarletteHTTPException
```

### 🏤-⚙️ **FastAPI**'Ⓜ ⚠ 🐕‍🦺

🚥 👆 💚 ⚙️ ⚠ ⤴️ ⏮️ 🎏 🔢 ⚠ 🐕‍🦺 ⚪️➡️ **FastAPI**, 👆 💪 🗄 & 🏤-⚙️ 🔢 ⚠ 🐕‍🦺 ⚪️➡️ `fastapi.exception_handlers`:

```Python hl_lines="2-5  15  21"
{!../../../docs_src/handling_errors/tutorial006.py!}
```

from starlette.exceptions import HTTPException as StarletteHTTPException
```

### **FastAPI** の例外ハンドラの再利用

また、何らかの方法で例外を使用することもできますが、**FastAPI** から同じデフォルトの例外ハンドラを使用することもできます。

デフォルトの例外ハンドラを`fastapi.exception_handlers`からインポートして再利用することができます:

```Python hl_lines="2 3 4 5 15 21"
{!../../../docs_src/handling_errors/tutorial006.py!}
```

この例では、非常に表現力のあるメッセージでエラーを`print`しています。

    assert response.json() == {"detail": "Item not found"}


def test_no_body_status_code_exception_handlers():
    response = client.get("/http-no-body-statuscode-exception")
    assert response.status_code == 204
    assert not response.content


def test_no_body_status_code_with_detail_exception_handlers():
    response = client.get("/http-no-body-statuscode-with-detail-exception")
    assert response.status_code == 204

    """

    async def custom_handler(websocket: WebSocket, exc: CustomError) -> None:
        await websocket.close(1002, "foo")

    myapp = make_app(exception_handlers={CustomError: custom_handler})
    client = TestClient(myapp)
    with pytest.raises(WebSocketDisconnect) as e:
        with client.websocket_connect("/custom_error/"):
            pass  # pragma: no cover

So, you will be able to see it all in the interactive API docs.

## Connect and disconnect

* Create your `FastAPI` application.
* Create event handlers to connect and disconnect from the database.

```Python hl_lines="42  45-47  50-52"
{!../../../docs_src/async_sql_databases/tutorial001.py!}
```

## Read notes

Create the *path operation function* to read notes:

        * [Override the default exception handlers](https://fastapi.tiangolo.com/tutorial/handling-errors/#override-the-default-exception-handlers).
        * [Re-use **FastAPI's** exception handlers](https://fastapi.tiangolo.com/tutorial/handling-errors/#re-use-fastapis-exception-handlers).
    * PR [#273](https://github.com/tiangolo/fastapi/pull/273).