FastAPI、SQLAlchemy、pytest，无法获得 100% 的覆盖率，未正确收集

Question

我正在尝试使用 python 3.9 构建完全覆盖测试的 FastAPI 应用程序为此，我选择了堆栈： FastAPI、uvicorn、SQLAlchemy、asyncpg、pytest（+ async、cov 插件）、coverage 和 httpx AsyncClient

这是我的最小值requirements.txt

所有测试运行顺利，我得到了预期的结果。但我遇到了问题，覆盖范围没有正确收集。它在第一个 await 关键字后中断，当协程 returns 控制回到事件循环

这里是关于如何重现此行为的最小集合 (it's also available on a GitHub)。

申请代码main.py:

import sqlalchemy as sa
from fastapi import FastAPI
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from starlette.requests import Request

app = FastAPI()
DATABASE_URL = 'sqlite+aiosqlite://?cache=shared'


@app.on_event('startup')
async def startup_event():
    engine = create_async_engine(DATABASE_URL, future=True)
    app.state.session = AsyncSession(engine, expire_on_commit=False)
    app.state.engine = engine


@app.on_event('shutdown')
async def shutdown_event():
    await app.state.session.close()


@app.get('/', name="home")
async def get_home(request: Request):
    res = await request.app.state.session.execute(sa.text('SELECT 1'))
    # after this line coverage breaks
    row = res.first()
    assert str(row[0]) == '1'
    return {"message": "OK"}

测试设置 conftest.py 如下所示：

import asyncio

import pytest
from asgi_lifespan import LifespanManager
from httpx import AsyncClient


@pytest.fixture(scope='session')
async def get_app():
    from main import app
    async with LifespanManager(app):
        yield app


@pytest.fixture(scope='session')
async def get_client(get_app):
    async with AsyncClient(app=get_app, base_url="http://testserver") as client:
        yield client


@pytest.fixture(scope="session")
def event_loop():
    loop = asyncio.new_event_loop()
    yield loop
    loop.close()

测试很简单（只需检查状态码为 200）test_main.py:

import pytest
from starlette import status


@pytest.mark.asyncio
async def test_view_health_check_200_ok(get_client):
    res = await get_client.get('/')
    assert res.status_code == status.HTTP_200_OK

pytest -vv --cov=. --cov-report term-missing --cov-report html

结果我得到：

Name           Stmts   Miss  Cover   Missing
--------------------------------------------
conftest.py       18      0   100%
main.py           20      3    85%   26-28
test_main.py       6      0   100%
--------------------------------------------
TOTAL             44      3    93%

上面的示例代码使用 aiosqlite 而不是 asyncpg 但覆盖失败也会持续重现
我断定这个问题出在 SQLAlchemy，因为这个使用 asyncpg 而不使用 SQLAlchemy 的例子就像 charm

Answer 1

这是 SQLAlchemy 1.4 在 coveragepy 中的一个问题：https://github.com/nedbat/coveragepy/issues/1082, https://github.com/nedbat/coveragepy/issues/1012

你可以试试 --concurrency==greenlet 选项

FastAPI、SQLAlchemy、pytest，无法获得 100% 的覆盖率，未正确收集

FastAPI, SQLAlchemy, pytest, unable to get 100% coverage, it doesn't properly collected

python

sqlalchemy

python-asyncio

pytest-asyncio

fastapi