pytest-asyncio RuntimeError: Cannot run the event loop while another loop is running - pytest

Question

When trying to do UI automtion with pytest-asyncio and pytest-playwright, I got exception like: RuntimeError: Cannot run the event loop while another loop is running
Code structure:
ui2/conftest.py
ui2/test_bing.py
ui2/conftest.py
import pytest
import asyncio
#pytest.fixture(scope="session")
def event_loop():
"""重写event_loop"""
loop = asyncio.get_event_loop()
yield loop
loop.close()
ui2/test_bing.py
import pytest
from playwright.async_api import Page
#pytest.mark.asyncio
async def test_bing(page: Page):
await page.goto("http://www.bing.com")
env:
pytest==7.1.2
pytest-asyncio==0.18.3
pytest-playwright==0.3.0
Detail exception as below:

Answer 1

Because you're importing from the async_api it sounds like you're writing asynchronous integration tests that you want to run concurrently. pytest-asyncio runs coroutine tests serially, so you instead want to use pytest-asyncio-cooperative. (If you wanted the tests run serially you should use from playwright.sync_api import Page.) I'd suggest:
Install pytest-asyncio-cooperative
pip install pytest-asyncio-cooperative
Remove event_loop fixture from ui2/conftest.py. pytest-asyncio-cooperative runs all test coroutines asynchronously on the same event loop implicitly.
Mark your async tests with #pytest.mark.asyncio_cooperative
import pytest
from playwright.async_api import Page
#pytest.mark.asyncio_cooperative
async def test_bing(page: Page):
await page.goto("http://www.bing.com")
Run your tests with the -p no:asyncio option. pytest-aysncio is not compatible with pytest-asyncio-cooperative, so it has to be disabled or uninstalled.
pytest -p no:asyncio

Answer 2

Short solution.
Install nest_asyncio:
pip install nest_asyncio
Then add this to your main conftest.py file:
import nest_asyncio
nest_asyncio.apply()
Find a more detailed explanation over here:
https://pypi.org/project/nest-asyncio/