由于对fastapi非常陌生，我正在努力测试比我在教程中看到的稍微困难一些的代码。我用 fastapi_cache 模块和redis如下：

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\u main.py如下所示：

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")

当我跑的时候 pytest ，设置 cache 变量到 None 测试失败。我想我明白为什么代码不起作用了。但是如何修复它以正确测试缓存呢？