@Override
  public long getStartTs() {
    return _startTs;
  }
@Test
  public void testGetStartTs() {
    MinionProgressObserver observer = new MinionProgressObserver(3);
    long ts1 = System.currentTimeMillis();
    observer.notifyTaskStart(null);
    long ts = observer.getStartTs();
    long ts2 = System.currentTimeMillis();
    assertTrue(ts1 <= ts);
    assertTrue(ts2 >= ts);
  }