def test_id(self):
        """
        Check that the id() of the doctests' case object contains the FQPN of
        the actual tests.
        """
        loader = runner.TestLoader()
        suite = loader.loadDoctests(mockdoctest)
        idPrefix = 'twisted.trial.test.mockdoctest.Counter'
        for test in suite._tests:
            self.assertIn(idPrefix, itrial.ITestCase(test).id())

        Check that the id() of the doctests' case object contains the FQPN of
        the actual tests.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_doctest.py