def test_runningWhenRunning(self):
        """
        L{Cooperator.running} reports C{True} when the L{Cooperator}
        is running.
        """
        c = task.Cooperator(started=False)
        c.start()
        self.addCleanup(c.stop)
        self.assertTrue(c.running)

        L{Cooperator.running} reports C{True} when the L{Cooperator}
        is running.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_cooperator.py