@Udf
  public Integer len(
      @UdfParameter(description = "The input string") final String input) {
    if (input == null) {
      return null;
    }
    return input.length();
  }
@Test
  public void shouldComputeLength() {
    final Integer result = udf.len("FoO bAr");
    assertThat(result, is(7));
  }