@Test
public void test_pinyin_only_contains_letters() throws Exception {

    Set<String> words = mDict.mapping().keySet();
    for (String word : words) {
        String[] pinyins = mDict.mapping().get(word);
        for (String pinyin : pinyins) {
            assertThat(pinyin.matches("[a-zA-Z]+"), is(true));
        }
    }
}