@Udf
  public String encodeParam(
      @UdfParameter(description = "the value to encode") final String input) {
    if (input == null) {
      return null;
    }
    final Escaper escaper = UrlEscapers.urlFormParameterEscaper();
    return escaper.escape(input);
  }
@Test
  public void shouldReturnEmptyStringForEmptyInput() {
    assertThat(encodeUdf.encodeParam(""), equalTo(""));
  }