],
)
def test_override_simple(url, status_code, expected):
    app.dependency_overrides[common_parameters] = overrider_dependency_simple
    response = client.get(url)
    assert response.status_code == status_code
    assert response.json() == expected
    app.dependency_overrides = {}


def test_override_with_sub_main_depends():
    app.dependency_overrides[common_parameters] = overrider_dependency_with_sub

        "data": [1, 2, 3],
    }


def test_override_data():
    app.dependency_overrides[get_data] = get_data_override
    response = client.get("/user")
    assert response.json() == {
        "user": "john",
        "scopes": ["foo", "bar"],
        "data": [3, 4, 5],
    }
    app.dependency_overrides = {}


def test_override_security():
    app.dependency_overrides[get_user] = get_user_override

    assert not override3 or "x-level3" in response.headers


@pytest.mark.parametrize("override1", [True, False])
@pytest.mark.parametrize("override2", [True, False])
@pytest.mark.parametrize("override3", [True, False])
@pytest.mark.parametrize("override4", [True, False])
@pytest.mark.parametrize("override5", [True, False])
def test_paths_level5(override1, override2, override3, override4, override5):

{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}
```

## Dependency override

Now we create the dependency override and add it to the overrides for our app.

```Python hl_lines="19-24  27"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}
```

!!! tip
    The code for `override_get_db()` is almost exactly the same as for `get_db()`, but in `override_get_db()` we use the `TestingSessionLocal` for the testing database instead.

```python
from fastapi import FastAPI
```

::: fastapi.FastAPI
    options:
        members:
            - openapi_version
            - webhooks
            - state
            - dependency_overrides
            - openapi
            - websocket
            - include_router
            - get
            - put
            - post
            - delete
            - options
            - head

    return {"message": "Hello Users!", "params": commons}


client = TestClient(app)


async def override_dependency(q: str | None = None):
    return {"q": q, "skip": 5, "limit": 10}


app.dependency_overrides[common_parameters] = override_dependency


def test_override_in_items():
    response = client.get("/items/")
    assert response.status_code == 200
    assert response.json() == {

from ...utils import needs_py310


@needs_py310
def test_override_in_items_run():
    from docs_src.dependency_testing.tutorial001_py310 import test_override_in_items

    test_override_in_items()


@needs_py310
def test_override_in_items_with_q_run():
    from docs_src.dependency_testing.tutorial001_py310 import (
        test_override_in_items_with_q,
    )

    test_override_in_items_with_q()


@needs_py310

常见实例是调用外部第三方身份验证应用。

向第三方应用发送令牌，然后返回经验证的用户。

但第三方服务商处理每次请求都可能会收费，并且耗时通常也比调用写死的模拟测试用户更长。

一般只要测试一次外部验证应用就够了，不必每次测试都去调用。

此时，最好覆盖调用外部验证应用的依赖项，使用返回模拟测试用户的自定义依赖项就可以了。

### 使用 `app.dependency_overrides` 属性

对于这些用例，**FastAPI** 应用支持 `app.dependcy_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。

```Python hl_lines="26-27  30"

👆 🎲 💚 💯 🔢 🐕‍🦺 🕐, ✋️ 🚫 🎯 🤙 ⚫️ 🔠 💯 👈 🏃.

👉 💼, 👆 💪 🔐 🔗 👈 🤙 👈 🐕‍🦺, & ⚙️ 🛃 🔗 👈 📨 🎁 👩‍💻, 🕴 👆 💯.

### ⚙️ `app.dependency_overrides` 🔢

👫 💼, 👆 **FastAPI** 🈸 ✔️ 🔢 `app.dependency_overrides`, ⚫️ 🙅 `dict`.

🔐 🔗 🔬, 👆 🚮 🔑 ⏮️ 🔗 (🔢), & 💲, 👆 🔗 🔐 (➕1️⃣ 🔢).

& ⤴️ **FastAPI** 🔜 🤙 👈 🔐 ↩️ ⏮️ 🔗.

```Python hl_lines="28-29  32"

def get_a_a_path_override():
    return "Hello A A"


@router_a_b_override.get("/")
def get_a_b():
    return "Hello A B"


@router_a_b_override.get("/override", response_class=HTMLResponse)
def get_a_b_path_override():
    return "Hello A B"


@router_b_override.get("/")
def get_b():
    return "Hello B"


@router_b_override.get("/override", response_class=HTMLResponse)
def get_b_path_override():