def test_runningWhenStopped(self):
        """
        L{Cooperator.running} reports C{False} after the L{Cooperator}
        has been stopped.
        """
        c = task.Cooperator(started=False)
        c.start()
        c.stop()
        self.assertFalse(c.running)

        L{Cooperator.running} reports C{False} after the L{Cooperator}
        has been stopped.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_cooperator.py