def test_testmoduleOnSourceAndTarget(self):
        """
        If --testmodule is specified twice, once for module A and once for
        a module which refers to module A, then make sure module A is only
        added once.
        """
        self.config.opt_testmodule(sibpath('moduletest.py'))
        self.config.opt_testmodule(sibpath('test_log.py'))
        self.assertSuitesEqual(trial._getSuite(self.config),
                               ['twisted.trial.test.test_log'])

        If --testmodule is specified twice, once for module A and once for
        a module which refers to module A, then make sure module A is only
        added once.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_script.py