def METHOD_NAME(self, multiverse):
    u = multiverse
    frames = []
    for frame in u.trajectory:
        pass
    # should rewind after previous test
    # problem was: the iterator is NoneType and next() cannot be called
    for ts in u.trajectory:
        frames.append(ts)
    assert_equal(
        len(frames), u.trajectory.n_frames,
        "iterated number of frames %d is not the expected number %d; "
        "trajectory iterator fails to rewind" %
        (len(frames), u.trajectory.n_frames))