@UdafFactory(description = "collect distinct values of a Bigint field into a single Array")
  public static <T> Udaf<T, List<T>, List<T>> createCollectSetT() {
    return new Collect<>();
  }
@Test
  public void shouldCollectDistinctTimestamps() {
    final Udaf<Timestamp, List<Timestamp>, List<Timestamp>> udaf = CollectSetUdaf.createCollectSetT();
    final Timestamp[] values = new Timestamp[] {new Timestamp(1), new Timestamp(2)};
    List<Timestamp> runningList = udaf.initialize();
    for (final Timestamp i : values) {
      runningList = udaf.aggregate(i, runningList);
    }
    assertThat(runningList, contains(new Timestamp(1), new Timestamp(2)));
  }