python - 如何在测试 FastAPI 应用程序时触发生命周期启动和关闭？

Question

作为 FastAPI 的新手，我正在努力测试比我在教程中看到的稍微困难的代码。我像这样使用 fastapi_cache 模块和 Redis:

from fastapi import Depends, FastAPI, Query, Request
from fastapi_cache.backends.redis import CACHE_KEY, RedisCacheBackend
from fastapi_cache import caches, close_caches

app = FastAPI()

def redis_cache():
    return caches.get(CACHE_KEY)    

@app.get('/cache')
async def test(
    cache: RedisCacheBackend = Depends(redis_cache),
    n: int = Query(
        ..., 
        gt=-1
    )
):  
    # code that uses redis cache

@app.on_event('startup')
async def on_startup() -> None:
    rc = RedisCacheBackend('redis://redis')
    caches.set(CACHE_KEY, rc)

@app.on_event('shutdown')
async def on_shutdown() -> None:
    await close_caches()

test_main.py 看起来像这样:

import pytest
from httpx import AsyncClient
from .main import app

@pytest.mark.asyncio
async def test_cache():
    async with AsyncClient(app=app, base_url="http://test") as ac:
        response = await ac.get("/cache?n=150")

当我运行 pytest 时，它将 cache 变量设置为 None 并且测试失败。我想我明白为什么代码不起作用。但是我该如何修复它以正确测试我的缓存？

Answer 1

重点是 httpx 没有实现生命周期协议(protocol)并触发 startup 事件处理程序。为此，您需要使用 LifespanManager。

安装:pip install asgi_lifespan

代码是这样的:

import pytest
from asgi_lifespan import LifespanManager
from httpx import AsyncClient
from .main import app


@pytest.mark.asyncio
async def test_cache():
    async with LifespanManager(app):
        async with AsyncClient(app=app, base_url="http://localhost") as ac:
            response = await ac.get("/cache")

更多信息在这里:https://github.com/encode/httpx/issues/350