def test_split_word_and_tone_none(): eq(('zi', None), pinyin.split_word_and_tone('zi'))
def test_split_word_and_tone_arabic_number(): eq(('2048', None), pinyin.split_word_and_tone('2048'))
def test_split_word_and_tone(): eq(('ai', 4), pinyin.split_word_and_tone('ai4'))