python runtime_error ai_generated true

RuntimeError: no running event loop

ID: python/pytest-asyncio-no-running-event-loop

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-06-04First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
0.21.x active — — —
0.23.x active — — —

Root Cause

An async test or fixture is executed without an active asyncio event loop. Typically pytest-asyncio mode is not configured, the test lacks @pytest.mark.asyncio, or the fixture is sync but awaits.

generic

中文

异步测试或 fixture 在没有活动 asyncio 事件循环的情况下执行。通常是 pytest-asyncio 模式未配置、测试缺少 @pytest.mark.asyncio 标记，或 fixture 是同步的却在 await。

Workarounds

  1. 93% success 
    # pyproject.toml
[tool.pytest.ini_options]
asyncio_mode = "auto"

# or pytest.ini
# [pytest]
# asyncio_mode = auto
  2. 90% success 
    import pytest, pytest_asyncio

@pytest_asyncio.fixture
async def client():
    async with AsyncClient() as c:
        yield c

@pytest.mark.asyncio
async def test_ping(client):
    r = await client.get('/ping')
    assert r.status_code == 200

Dead Ends

Common approaches that don't work:

  1. 70% fail

    pytest-asyncio already manages the loop; nested asyncio.run raises 'asyncio.run() cannot be called from a running event loop' or double-closes the loop.

  2. 65% fail

    Sync fixtures cannot yield awaited values; the coroutine object is returned instead of the resolved value, causing the exact error downstream.