您已经了解了如何使用 `TestClient` 测试 **FastAPI** 应用程序。但是到目前为止，您只了解了如何编写同步测试，而没有使用 `async` 异步函数。

在测试中能够使用异步函数可能会很有用，比如当您需要异步查询数据库的时候。想象一下，您想要测试向 FastAPI 应用程序发送请求，然后验证您的后端是否成功在数据库中写入了正确的数据，与此同时您使用了异步的数据库的库。

让我们看看如何才能实现这一点。

## pytest.mark.anyio { #pytest-mark-anyio }

如果我们想在测试中调用异步函数，那么我们的测试函数必须是异步的。 AnyIO 为此提供了一个简洁的插件，它允许我们指定一些测试函数要异步调用。

## HTTPX { #httpx }

即使您的 **FastAPI** 应用程序使用普通的 `def` 函数而不是 `async def` ，它本质上仍是一个 `async` 异步应用程序。

        "type": "object",
    }


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_missing(path: str):
    client = TestClient(app)
    response = client.post(path)
    assert response.status_code == 200
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)

class QueryModelRequiredStr(BaseModel):
    p: str


@app.get("/model-required-str")
async def read_model_required_str(p: Annotated[QueryModelRequiredStr, Query()]):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/required-str", "/model-required-str"],
)
def test_required_str_schema(path: str):
    assert app.openapi()["paths"][path]["get"]["parameters"] == snapshot(
        [
            {

        "type": "object",
    }


@pytest.mark.parametrize(
    "path",
    [
        "/optional-bytes",
        "/optional-uploadfile",
    ],
)
def test_optional_missing(path: str):
    client = TestClient(app)
    response = client.post(path)
    assert response.status_code == 200, response.text
    assert response.json() == {"file_size": None}


@pytest.mark.parametrize(
    "path",
    [

    p: str


@app.post("/model-required-str", operation_id="model_required_str")
async def read_model_required_str(p: Annotated[FormModelRequiredStr, Form()]):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/required-str", "/model-required-str"],
)
def test_required_str_schema(path: str):
    openapi = app.openapi()
    body_model_name = get_body_model_name(openapi, path)

            }
        ]
    )


@pytest.mark.parametrize(
    "path",
    ["/optional-list-str", "/model-optional-list-str"],
)
def test_optional_list_str_missing(path: str):
    client = TestClient(app)
    response = client.get(path)
    assert response.status_code == 200, response.text
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",

@app.post("/list-uploadfile", operation_id="list_uploadfile")
async def read_list_uploadfile(p: Annotated[list[UploadFile], File()]):
    return {"file_size": [file.size for file in p]}


@pytest.mark.parametrize(
    "path",
    [
        "/list-bytes",
        "/list-uploadfile",
    ],
)
def test_list_schema(path: str):
    openapi = app.openapi()
    body_model_name = get_body_model_name(openapi, path)

    p: list[str]


@app.get("/model-required-list-str")
def read_model_required_list_str(p: Annotated[HeaderModelRequiredListStr, Header()]):
    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/required-list-str", "/model-required-list-str"],
)
def test_required_list_str_schema(path: str):
    assert app.openapi()["paths"][path]["get"]["parameters"] == snapshot(
        [

        "type": "object",
    }


@pytest.mark.parametrize(
    "path",
    ["/optional-list-str", "/model-optional-list-str"],
)
def test_optional_list_str_missing(path: str):
    client = TestClient(app)
    response = client.post(path)
    assert response.status_code == 200, response.text
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",

@pytest.mark.parametrize(
    "value,code",
    [
        ("-1", 200),
        ("inf", 200),
        ("-inf", 200),
        ("nan", 200),
        ("0", 200),
        ("342", 200),
    ],
)
def test_allow_inf_nan_param_default(value: str, code: int):
    response = client.post(f"/?z={value}")
    assert response.status_code == code, response.text


@pytest.mark.parametrize(
    "value,code",