def test_initialState(self):
        """
        L{Automaton.initialState} is a descriptor that sets the initial
        state if it's not yet set, and raises L{ValueError} if it is.

        """
        a = Automaton()
        a.initialState = "a state"
        self.assertEqual(a.initialState, "a state")
        with self.assertRaises(ValueError):
            a.initialState = "another state"

        L{Automaton.initialState} is a descriptor that sets the initial
        state if it's not yet set, and raises L{ValueError} if it is.

        
stackoverflow/venv/lib/python3.6/site-packages/automat/_test/test_core.py