def test_runnerDebuggerWithExplicitlyPassedPdb(self):
        """
        Trial uses pdb if pdb is passed explicitly to the `--debugger` arg.
        """
        self.parseOptions([
            '--reporter', 'capturing',
            '--debugger', 'pdb',
            '--debug', 'twisted.trial.test.sample',
        ])

        self.runcall_called = False
        def runcall(pdb, suite, result):
            self.runcall_called = True
        self.patch(pdb.Pdb, "runcall", runcall)

        self.runSampleSuite(self.getRunner())

        self.assertTrue(self.runcall_called)

        Trial uses pdb if pdb is passed explicitly to the `--debugger` arg.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_runner.py