### Use the `app.dependency_overrides` attribute

For these cases, your **FastAPI** application has an attribute `app.dependency_overrides`, it is a simple `dict`.

To override a dependency for testing, you put as a key the original dependency (a function), and as the value, your dependency override (another function).

And then **FastAPI** will call that override instead of the original dependency.

//// tab | Python 3.10+

#!/usr/bin/env bash
set -x

ruff check fastapi tests docs_src scripts --fix

///

## O principal `FastAPI`

Agora, vamos ver o módulo em `app/main.py`.

Aqui é onde você importa e usa a classe `FastAPI`.

Este será o arquivo principal em seu aplicativo que une tudo.

E como a maior parte de sua lógica agora viverá em seu próprio módulo específico, o arquivo principal será bem simples.

### Importar `FastAPI`

Você importa e cria uma classe `FastAPI` normalmente.

{!../../docs_src/query_params/tutorial002.py!}
```

이 경우 함수 매개변수 `q`는 선택적이며 기본값으로 `None` 값이 됩니다.

/// check | "확인"

**FastAPI**는 `item_id`가 경로 매개변수이고 `q`는 경로 매개변수가 아닌 쿼리 매개변수라는 것을 알 정도로 충분히 똑똑합니다.

///

/// note | "참고"

FastAPI는 `q`가 `= None`이므로 선택적이라는 것을 인지합니다.

`Union[str, None]`에 있는 `Union`은 FastAPI(FastAPI는 `str` 부분만 사용합니다)가 사용하는게 아니지만, `Union[str, None]`은 편집기에게 코드에서 오류를 찾아낼 수 있게 도와줍니다.

///

## 쿼리 매개변수 형변환

from typing import Optional

import pytest
from dirty_equals import IsDict
from fastapi import APIRouter, Depends, FastAPI
from fastapi.testclient import TestClient

app = FastAPI()

router = APIRouter()


async def common_parameters(q: str, skip: int = 0, limit: int = 100):
    return {"q": q, "skip": skip, "limit": limit}


@app.get("/main-depends/")
async def main_depends(commons: dict = Depends(common_parameters)):

import pytest
from fastapi.testclient import TestClient

from ...utils import needs_pydanticv1


@pytest.fixture(name="client")
def get_client():
    from docs_src.schema_extra_example.tutorial001_pv1 import app

    client = TestClient(app)
    return client


@needs_pydanticv1
def test_post_body_example(client: TestClient):
    response = client.put(
        "/items/5",
        json={
            "name": "Foo",

import pytest
from dirty_equals import IsDict
from fastapi.testclient import TestClient

from ...utils import needs_py310


@pytest.fixture(name="client")
def get_client():
    from docs_src.query_params_str_validations.tutorial011_py310 import app

    client = TestClient(app)
    return client


@needs_py310
def test_multi_query_values(client: TestClient):
    url = "/items/?q=foo&q=bar"
    response = client.get(url)

import pytest
from dirty_equals import IsDict
from fastapi.testclient import TestClient

from ...utils import needs_py39


@pytest.fixture(name="client")
def get_client():
    from docs_src.query_params_str_validations.tutorial011_py39 import app

    client = TestClient(app)
    return client


@needs_py39
def test_multi_query_values(client: TestClient):
    url = "/items/?q=foo&q=bar"
    response = client.get(url)

import pytest
from dirty_equals import IsDict
from fastapi.testclient import TestClient


@pytest.fixture(name="client")
def get_client():
    from docs_src.body_multiple_params.tutorial003_an import app

    client = TestClient(app)
    return client


def test_post_body_valid(client: TestClient):
    response = client.put(
        "/items/5",
        json={
            "importance": 2,

import pytest
from dirty_equals import IsDict
from fastapi.testclient import TestClient

from ...utils import needs_py310


@pytest.fixture(name="client")
def get_client():
    from docs_src.body_multiple_params.tutorial003_an_py310 import app

    client = TestClient(app)
    return client


@needs_py310
def test_post_body_valid(client: TestClient):
    response = client.put(
        "/items/5",
        json={