@Test
public void testPollAll() {

  LOG.info("Test poll all");
  for (Integer i : list) {
    assertTrue(set.add(i));
  }
  // remove all elements by polling
  while (set.pollFirst() != null);
  assertEquals(0, set.size());
  assertTrue(set.isEmpty());
  // the deleted elements should not be there
  for (int i = 0; i < NUM; i++) {
    assertFalse(set.contains(list.get(i)));
  }
  Iterator<Integer> iter = set.iterator();
  assertFalse(iter.hasNext());
  LOG.info("Test poll all - DONE");
}