Asynchronous testing with unittest RuntimeError

I'm kind of a beginner with testing my code in Python, and I'm trying to test an API "wrapper" I created (working with Riot's API) with unittest.IsolatedAsyncioTestCase, and I have an error that says :

Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x000002511047C160>
Traceback (most recent call last):
  File "C:\Program Files\Python39\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "C:\Program Files\Python39\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "C:\Program Files\Python39\lib\asyncio\base_events.py", line 746, in call_soon
    self._check_closed()
  File "C:\Program Files\Python39\lib\asyncio\base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed
Exception ignored in: <function _ProactorBasePipeTransport.__del__ at 0x000002511047C160>
Traceback (most recent call last):
  File "C:\Program Files\Python39\lib\asyncio\proactor_events.py", line 116, in __del__
    self.close()
  File "C:\Program Files\Python39\lib\asyncio\proactor_events.py", line 108, in close
    self._loop.call_soon(self._call_connection_lost, None)
  File "C:\Program Files\Python39\lib\asyncio\base_events.py", line 746, in call_soon
    self._check_closed()
  File "C:\Program Files\Python39\lib\asyncio\base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

This error is after the test is finished since I have "Run 2 tests OK" just before.

Here is a simplified version of my code :

class TestMyMethods(unittest.IsolatedAsyncioTestCase):
    
    def setUp(self):
        """Setting up the tests"""
        # Loading dotenv
        load_dotenv(dotenv_path=Path('.') / '.env')

        # Initializing MyWrapper
        self.mongo_client = MongoClient()
        self.db = self.mongo_client["test-database"]
        self.my_wrapper = MyWrapper(os.getenv("RIOT_API_KEY"), self.db)

    async def test_get_summoner(self):
        x = await self.grasp.grasp_summoner_data("SummonerName")
        self.assertEqual(x["name"], "SummonerName")

if __name__ == '__main__':
    with warnings.catch_warnings():
        warnings.simplefilter("ignore")
        unittest.main()

I can't find any clue of what's happening and what am I doing wrong, and there is not much documentation for this on the Internet.

Thanks for you help !