def test_decorateDecoratedSuite(self):
        """
        Calling L{decorate} on a test suite with already-decorated tests
        decorates all of the tests in the suite again.
        """
        test = self.TestCase()
        decoratedTest = unittest.decorate(test, unittest.TestDecorator)
        redecoratedTest = unittest.decorate(decoratedTest,
                                            unittest.TestDecorator)
        self.assertTestsEqual(redecoratedTest,
                              unittest.TestDecorator(decoratedTest))

        Calling L{decorate} on a test suite with already-decorated tests
        decorates all of the tests in the suite again.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_tests.py