@pytest.fixture(params=[pytest.param(MulTbArgs())], ids=mul_tb_id)
def mul_tb(mod, request):
    """The multiplier testbench proper. Receives arguments via request."""
    async def testbench(s):
        m = mod

        if m.registered:
            await s.tick()
        else:
            await s.delay(0.1)

        s.set(m.a, request.param.a_in)
        s.set(m.b, request.param.b_in)

        if m.registered:
            await s.tick()
        else:
            await s.delay(0.1)

        # assert s.get(m.o) == request.param.o_out
        assert (yield m.o) == request.param.o_out

    return testbench