Lists.newArrayList(1, 2),
            Lists.newArrayList(1),
            Lists.newArrayList(2),
            Lists.newArrayList(),
            null)
        .inOrder();
  }

  public void testNatural() {
    Ordering<Integer> comparator = Ordering.natural();
    Helpers.testComparator(comparator, Integer.MIN_VALUE, -1, 0, 1, Integer.MAX_VALUE);
    try {
      comparator.compare(1, null);
      fail();