@Udf
  public String ucase(
      @UdfParameter(description = "The string to upper-case") final String input) {
    if (input == null) {
      return null;
    }
    return input.toUpperCase();
  }
@Test
  public void shouldReturnNullForNullInput() {
    final String result = udf.ucase(null);
    assertThat(result, is(nullValue()));
  }