def test_chop_does_simulation_correct(self):
        r = pyrtl.Register(5, 'r')
        r.next <<= r + 1
        a, b, c = pyrtl.helperfuncs.chop(r, 2, 2, 1)
        o = pyrtl.Output(name='o')
        o <<= c
        self.check_trace('o 01010101\nr 01234567\n')