import pytest
from fastapi import APIRouter, FastAPI
from fastapi.routing import APIRoute
from fastapi.testclient import TestClient
from inline_snapshot import snapshot
from starlette.routing import Route

app = FastAPI()


class APIRouteA(APIRoute):
    x_type = "A"


class APIRouteB(APIRoute):
    x_type = "B"


class APIRouteC(APIRoute):
    x_type = "C"


router_a = APIRouter(route_class=APIRouteA)

**FastAPI** アプリケーションが通常の `def` 関数を使っていても、その内側は依然として `async` アプリケーションです。

`TestClient` は、標準の pytest を使って通常の `def` のテスト関数から非同期の FastAPI アプリを呼び出すための「おまじない」を内部で行います。しかし、その「おまじない」はテスト関数自体が非同期の場合には機能しません。テストを非同期で実行すると、テスト関数内で `TestClient` は使えなくなります。

`TestClient` は [HTTPX](https://www.python-httpx.org) を基に作られており、幸いなことに API のテストには HTTPX を直接利用できます。

## 例 { #example }

from typing import TYPE_CHECKING, Annotated

from fastapi import Depends, FastAPI
from fastapi.testclient import TestClient

from .utils import needs_py314

if TYPE_CHECKING:  # pragma: no cover

    class DummyUser: ...


@needs_py314
def test_stringified_annotation():
    # python3.14: Use forward reference without "from __future__ import annotations"
    async def get_current_user() -> DummyUser | None:
        return None

from typing import Annotated

import pytest
from fastapi import FastAPI, Query
from fastapi.exceptions import FastAPIDeprecationWarning
from fastapi.testclient import TestClient
from inline_snapshot import snapshot

from .utils import needs_py310


def get_client():
    app = FastAPI()
    with pytest.warns(FastAPIDeprecationWarning):

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

from typing import Annotated

from fastapi import FastAPI, Form
from fastapi.testclient import TestClient
from pydantic import BaseModel, Field

app = FastAPI()


class FormModel(BaseModel):
    username: str
    lastname: str
    age: int | None = None
    tags: list[str] = ["foo", "bar"]
    alias_with: str = Field(alias="with", default="nothing")


class FormModelExtraAllow(BaseModel):
    param: str

from fastapi.testclient import TestClient
from inline_snapshot import snapshot

from docs_src.behind_a_proxy.tutorial003_py310 import app

client = TestClient(app)


def test_main():
    response = client.get("/app")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World", "root_path": "/api/v1"}


def test_openapi_schema():
    response = client.get("/openapi.json")

# Ref: https://github.com/tiangolo/fastapi/issues/5623

from typing import Annotated, Any

from fastapi import FastAPI, Security
from fastapi.security import SecurityScopes
from fastapi.testclient import TestClient


async def security1(scopes: SecurityScopes):
    return scopes.scopes


async def security2(scopes: SecurityScopes):
    return scopes.scopes


async def dep3(

from fastapi import Depends, FastAPI
from fastapi.security import HTTPBearer
from fastapi.testclient import TestClient
from inline_snapshot import snapshot

app = FastAPI()

bearer_scheme = HTTPBearer()


@app.get("/", dependencies=[Depends(bearer_scheme)])
async def get_root():
    return {"message": "Hello, World!"}


client = TestClient(app)


def test_get_root():

from unittest.mock import patch

from fastapi import FastAPI
from fastapi.responses import JSONResponse
from fastapi.testclient import TestClient
from pydantic import BaseModel


class Item(BaseModel):
    name: str
    price: float


app = FastAPI()


@app.get("/default")
def get_default() -> Item:
    return Item(name="widget", price=9.99)


@app.get("/explicit", response_class=JSONResponse)

from fastapi import Depends, FastAPI, Security
from fastapi.security import APIKeyHeader
from fastapi.testclient import TestClient
from inline_snapshot import snapshot
from pydantic import BaseModel

app = FastAPI()

api_key = APIKeyHeader(name="key")


class User(BaseModel):
    username: str


def get_current_user(oauth_header: str = Security(api_key)):
    user = User(username=oauth_header)
    return user