В этом случае вам может понадобиться задокументировать, как должно выглядеть это внешнее API: какую *операцию пути* оно должно иметь, какое тело запроса ожидать, какой ответ возвращать и т.д.

## Приложение с обратными вызовами { #an-app-with-callbacks }

Давайте рассмотрим это на примере.

Представьте, что вы разрабатываете приложение, позволяющее создавать счета.

Эти счета будут иметь `id`, `title` (необязательный), `customer` и `total`.

        importlib.reload(mod)
    mod.sqlite_url = "sqlite://"
    mod.engine = create_engine(
        mod.sqlite_url, connect_args={"check_same_thread": False}, poolclass=StaticPool
    )

    with TestClient(mod.app) as c:
        yield c
    # Clean up connection explicitly to avoid resource warning
    mod.engine.dispose()


def test_crud_app(client: TestClient):

Pero si necesitas acceder a variables y objetos de la misma app de **FastAPI**, o necesitas realizar pequeñas tareas en segundo plano (como enviar una notificación por email), simplemente puedes usar `BackgroundTasks`.

## Resumen { #recap }

Muitos erros exóticos durante a instalação de um pacote são resolvidos apenas atualizando o `pip` primeiro.

/// tip | Dica

Normalmente, você faria isso **uma vez**, logo após criar o ambiente virtual.

///

Certifique-se de que o ambiente virtual esteja ativo (com o comando acima) e execute:

<div class="termy">

```console
$ python -m pip install --upgrade pip

        pytest.param("tutorial004_py310", marks=needs_py310),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.body.{request.param}")

    client = TestClient(mod.app)
    return client


def test_put_all(client: TestClient):
    response = client.put(
        "/items/123",
        json={"name": "Foo", "price": 50.1, "description": "Some Foo", "tax": 0.3},

    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.dependencies.{request.param}")

    client = TestClient(mod.app)
    return client


@pytest.mark.parametrize(
    "path,expected_status,expected_response",
    [
        (
            "/items",
            200,
            {
                "items": [

    module = importlib.import_module(f"docs_src.encoder.{request.param}")
    return module


@pytest.fixture(name="client")
def get_client(mod: ModuleType):
    client = TestClient(mod.app)
    return client


def test_put(client: TestClient, mod: ModuleType):
    fake_db = mod.fake_db

    response = client.put(
        "/items/123",
        json={
            "title": "Foo",

    ],
)
def get_client(request: pytest.FixtureRequest) -> TestClient:
    mod = importlib.import_module(
        f"docs_src.path_params_numeric_validations.{request.param}"
    )
    return TestClient(mod.app)


@pytest.mark.parametrize(
    "path,expected_response",
    [
        ("/items/42?q=", {"item_id": 42}),
        ("/items/1?q=somequery", {"item_id": 1, "q": "somequery"}),
    ],
)

        "tutorial001_an_py39",
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.request_form_models.{request.param}")

    client = TestClient(mod.app)
    return client


def test_post_body_form(client: TestClient):
    response = client.post("/login/", data={"username": "Foo", "password": "secret"})
    assert response.status_code == 200

        "tutorial001_an_py39",
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.request_forms.{request.param}")

    client = TestClient(mod.app)
    return client


def test_post_body_form(client: TestClient):
    response = client.post("/login/", data={"username": "Foo", "password": "secret"})
    assert response.status_code == 200