def test_decoratePreservesSuite(self):
        """
        Tests can be in non-standard suites. L{decorate} preserves the
        non-standard suites when it decorates the tests.
        """
        test = self.TestCase()
        suite = runner.DestructiveTestSuite([test])
        decorated = unittest.decorate(suite, unittest.TestDecorator)
        self.assertSuitesEqual(
            decorated,
            runner.DestructiveTestSuite([unittest.TestDecorator(test)]))

        Tests can be in non-standard suites. L{decorate} preserves the
        non-standard suites when it decorates the tests.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_tests.py