def test_bitfield_all_but_lsb(self):
        a = pyrtl.Const(0, 8)
        pyrtl.probe(pyrtl.bitfield_update(a, 1, None, 0b1011101), 'out')  # TODO
        sim = pyrtl.Simulation()
        sim.step({})
        self.assertEqual(sim.inspect('out'), 0b10111010)