def METHOD_NAME(test_dir, num=10, seed=0):
    """generate feature matrices."""
    expected_feats = {}
    np.random.seed(seed)
    utt_ids, rxfiles, utt2num_frames = [], [], []
    for i in range(num):
        utt_id = "utt_id_" + str(i)
        ark_file = os.path.join(test_dir, "mat_" + str(i) + ".ark")
        length = np.random.randint(200, 800)
        m = np.random.uniform(-10.0, 10.0, (length, 40))
        expected_feats[utt_id] = m
        kaldi_io.write_mat(ark_file, m)
        utt_ids.append(utt_id)
        rxfiles.append(ark_file + ":0")
        utt2num_frames.append(length)
    return expected_feats, utt_ids, rxfiles, utt2num_frames