### 使用 `app.dependency_overrides` 属性

对于这些用例，**FastAPI** 应用支持 `app.dependency_overrides` 属性，该属性就是**字典**。

要在测试时覆盖原有依赖项，这个字典的键应当是原依赖项（函数），值是覆盖依赖项（另一个函数）。

这样一来，**FastAPI** 就会调用覆盖依赖项，不再调用原依赖项。

{* ../../docs_src/dependency_testing/tutorial001_an_py310.py hl[26:27,30] *}

/// tip | 提示

**FastAPI** 应用中的任何位置都可以实现覆盖依赖项。

原依赖项可用于*路径操作函数*、*路径操作装饰器*（不需要返回值时）、`.include_router()` 调用等。

FastAPI 可以覆盖这些位置的依赖项。

///

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/")
def read_items():

///

/// note | 기술 세부사항

`from starlette.testclient import TestClient` 역시 사용할 수 있습니다.

**FastAPI** 는 개발자의 편의를 위해 `starlette.testclient` 를 `fastapi.testclient` 로도 제공할 뿐입니다. 이는 단지 `Starlette` 에서 직접 가져오는지의 차이일 뿐입니다.

///

/// tip | 팁

FastAPI 애플리케이션에 요청을 보내는 것 외에도 테스트에서 `async` 함수를 호출하고 싶다면 (예: 비동기 데이터베이스 함수), 심화 튜토리얼의 [Async Tests](../advanced/async-tests.md){.internal-link target=_blank} 를 참조하세요.

返回的响应如下：

```JSON
{
    "message": "Hello World",
    "root_path": "/api/v1"
}
```

### 在 FastAPI 应用里设置 `root_path`

还有一种方案，如果不能提供 `--root-path` 或等效的命令行选项，则在创建 FastAPI 应用时要设置 `root_path` 参数。

{* ../../docs_src/behind_a_proxy/tutorial002.py hl[3] *}

传递 `root_path` 给 `FastAPI` 与传递 `--root-path` 命令行选项给 Uvicorn 或 Hypercorn 一样。

### 关于 `root_path`

注意，服务器（Uvicorn）只是把 `root_path` 传递给应用。

from typing import Union

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: set[str] = set()


@app.post(
    "/items/",
    response_model=Item,
    summary="Create an item",
    response_description="The created item",
)

/// note | Hinweis

FastAPI weiß, dass der Wert von `q` nicht erforderlich ist, aufgrund des definierten Defaultwertes `= None`.

Das `str | None` (Python 3.10+) oder `Union` in `Union[str, None]` (Python 3.9+) wird von FastAPI nicht verwendet, um zu bestimmen, dass der Wert nicht erforderlich ist. FastAPI weiß, dass er nicht erforderlich ist, weil er einen Defaultwert von `= None` hat.

from fastapi import FastAPI

from . import a, b

app = FastAPI()

app.include_router(a.router, prefix="/a")

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/", openapi_extra={"x-aperture-labs-portal": "blue"})
async def read_items():

To configure them, pass the `swagger_ui_parameters` argument when creating the `FastAPI()` app object or to the `get_swagger_ui_html()` function.

`swagger_ui_parameters` receives a dictionary with the configurations passed to Swagger UI directly.

FastAPI converts the configurations to **JSON** to make them compatible with JavaScript, as that's what Swagger UI needs.

keystone:
  - url: https://fastapicloud.com
    title: FastAPI Cloud. By the same team behind FastAPI. You code. We Cloud.
    img: https://fastapi.tiangolo.com/img/sponsors/fastapicloud.png
gold:
  - url: https://blockbee.io?ref=fastapi
    title: BlockBee Cryptocurrency Payment Gateway
    img: https://fastapi.tiangolo.com/img/sponsors/blockbee.png
  - url: https://github.com/scalar/scalar/?utm_source=fastapi&utm_medium=website&utm_campaign=main-badge