public void test_addNullNormalizer() throws Exception {
        NormalizerChain chain = new NormalizerChain();
        chain.add(null);
    }

    @Test
    public void test_chainWithNormalizerReturningNull() throws Exception {
        NormalizerChain chain = new NormalizerChain();
        chain.add((text, field, langs) -> null);
        chain.add((text, field, langs) -> text.toUpperCase());