@Udf
  public String extractFragment(
      @UdfParameter(
          value = "input",
          description = "a valid URL to extract a fragment from")
      final String input) {
    return UrlParser.extract(input, URI::getFragment);
  }
@Test
  public void shouldReturnNullIfNoFragment() {
    assertThat(extractUdf.extractFragment("https://docs.confluent.io/current/ksql/docs/syntax-reference.html"), nullValue());
  }