def test_addSkipSendsSubunitAddSkip(self):
        """
        Some versions of subunit have "addSkip". For these versions, when we
        call 'addSkip' on the test result, we pass the test and reason through
        to the subunit client.
        """
        addSkipCalls = []
        def addSkip(test, reason):
            addSkipCalls.append((test, reason))

        # Provide our own addSkip, whether or not the locally-installed
        # subunit has addSkip.
        self.result._subunit.addSkip = addSkip
        self.result.addSkip(self.test, 'reason')
        self.assertEqual(addSkipCalls, [(self.test, 'reason')])

        Some versions of subunit have "addSkip". For these versions, when we
        call 'addSkip' on the test result, we pass the test and reason through
        to the subunit client.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_reporter.py