def test_postClassCleanupNoErrors(self):
        """
        The post-class cleanup method will not call C{addError} on the result
        if there are no pending calls or selectables.
        """
        reactor = StubReactor([])
        test = object()
        reporter = StubErrorReporter()
        jan = _Janitor(test, reporter, reactor=reactor)
        jan.postClassCleanup()
        self.assertEqual(reporter.errors, [])

        The post-class cleanup method will not call C{addError} on the result
        if there are no pending calls or selectables.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_util.py