"openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/items/{item_id}": {
                "get": {
                    "responses": {
                        "404": {"description": "Item not found"},
                        "302": {"description": "The item was moved"},
                        "403": {"description": "Not enough privileges"},
                        "200": {

The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException`

To return HTTP responses with errors to the client you use `HTTPException`.

### Import `HTTPException`

```Python hl_lines="1"

    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:

    client = TestClient(app)
    return client


@needs_py39
def test_get_no_item(client: TestClient):
    response = client.get("/items/foo")
    assert response.status_code == 404, response.text
    assert response.json() == {"detail": "Item not found, there's only a plumbus here"}


@needs_py39
def test_get(client: TestClient):
    response = client.get("/items/plumbus")

**FastAPI** nimmt dieses Modell, generiert dessen JSON-Schema und fügt es an der richtigen Stelle in OpenAPI ein.

Um beispielsweise eine weitere Response mit dem Statuscode `404` und einem Pydantic-Modell `Message` zu deklarieren, können Sie schreiben:

```Python hl_lines="18  22"
{!../../docs_src/additional_responses/tutorial001.py!}
```

/// note | "Hinweis"

**FastAPI** will take that model, generate its JSON Schema and include it in the correct place in OpenAPI.

For example, to declare another response with a status code `404` and a Pydantic model `Message`, you can write:

{* ../../docs_src/additional_responses/tutorial001.py hl[18,22] *}

/// note

Keep in mind that you have to return the `JSONResponse` directly.

///

/// info

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

Wenn Sie dann zu den URLs unter `/openapi.json`, `/docs` oder `/redoc` gehen, erhalten Sie lediglich einen `404 Not Found`-Fehler, wie:

```JSON
{
    "detail": "Not Found"
}

    response = client.post("/users/rick")
    assert response.status_code == 405, response.text


def test_invalid_path_doesnt_match():
    response = client.post("/usersx/rick")
    assert response.status_code == 404, response.text


def test_websocket():
    with client.websocket_connect("/items/portal-gun") as websocket:
        data = websocket.receive_json()

        assert response.json() == snapshot({"ok": True})

        response = client.get(f"/heroes/{hero_id}")
        assert response.status_code == 404, response.text

        response = client.delete(f"/heroes/{hero_id}")
        assert response.status_code == 404, response.text
        assert response.json() == snapshot({"detail": "Hero not found"})


def test_openapi_schema(client: TestClient):

        # The hero is no longer found
        response = client.get(f"/heroes/{hero_id}")
        assert response.status_code == 404, response.text

        # Delete a hero that does not exist
        response = client.delete(f"/heroes/{hero_id}")
        assert response.status_code == 404, response.text
        assert response.json() == snapshot({"detail": "Hero not found"})

        # Update a hero that does not exist