test_main.py 文件源码

def setUp(self):
        old_log_level = log.getEffectiveLevel()
        self.addCleanup(log.setLevel, old_log_level)
        self.resources = ExitStack()
        # Create a new event loop, and arrange for that loop to end almost
        # immediately.  This will allow the calls to main() in these tests to
        # also exit almost immediately.  Otherwise, the foreground test
        # process will hang.
        #
        # I think this introduces a race condition.  It depends on whether the
        # call_later() can possibly run before the run_forever() does, or could
        # cause it to not complete all its tasks.  In that case, you'd likely
        # get an error or warning on stderr, which may or may not cause the
        # test to fail.  I've only seen this happen once and don't have enough
        # information to know for sure.
        default_loop = asyncio.get_event_loop()
        loop = asyncio.new_event_loop()
        loop.call_later(0.1, loop.stop)
        self.resources.callback(asyncio.set_event_loop, default_loop)
        asyncio.set_event_loop(loop)
        self.addCleanup(self.resources.close)