@Udf(description = "Returns the current number of days for the system since "
      + "1970-01-01 00:00:00 UTC/GMT.")
  public int unixDate() {
    return ((int) LocalDate.now().toEpochDay());
  }
@Test
  public void shouldReturnNull() {
    // When:
    final Integer result = udf.unixDate(null);

    // Then:
    assertNull(result);
  }