def METHOD_NAME(dataset_dir):
    """
    dataset_dir: directory to the mocked dataset
    """
    mocked_samples = []
    mocked_train_samples = []
    mocked_valid_samples = []
    mocked_test_samples = []
    os.makedirs(dataset_dir, exist_ok=True)
    sample_rate = 16000  # 16kHz sample rate
    seed = 0
    valid_file = os.path.join(dataset_dir, "validation_list.txt")
    test_file = os.path.join(dataset_dir, "testing_list.txt")
    with open(valid_file, "w") as valid, open(test_file, "w") as test:
        for label in _LABELS:
            path = os.path.join(dataset_dir, label)
            os.makedirs(path, exist_ok=True)
            for j in range(6):
                # generate hash ID for speaker
                speaker = "{:08x}".format(j)
                for utterance in range(3):
                    filename = f"{speaker}{speechcommands.HASH_DIVIDER}{utterance}.wav"
                    file_path = os.path.join(path, filename)
                    seed += 1
                    data = get_whitenoise(
                        sample_rate=sample_rate,
                        duration=0.01,
                        n_channels=1,
                        dtype="int16",
                        seed=seed,
                    )
                    save_wav(file_path, data, sample_rate)
                    sample = (
                        normalize_wav(data),
                        sample_rate,
                        label,
                        speaker,
                        utterance,
                    )
                    mocked_samples.append(sample)
                    if j < 2:
                        mocked_train_samples.append(sample)
                    elif j < 4:
                        valid.write(f"{label}/{filename}\n")
                        mocked_valid_samples.append(sample)
                    elif j < 6:
                        test.write(f"{label}/{filename}\n")
                        mocked_test_samples.append(sample)
    return mocked_samples, mocked_train_samples, mocked_valid_samples, mocked_test_samples