private final Ordering<Number> numberOrdering = new NumberOrdering();

  public void testAllEqual() {
    Ordering<@Nullable Object> comparator = Ordering.allEqual();
    assertThat(comparator.reverse()).isSameInstanceAs(comparator);

    assertEquals(0, comparator.compare(null, null));
    assertEquals(0, comparator.compare(new Object(), new Object()));

  private final Ordering<Number> numberOrdering = new NumberOrdering();

  public void testAllEqual() {
    Ordering<@Nullable Object> comparator = Ordering.allEqual();
    assertThat(comparator.reverse()).isSameInstanceAs(comparator);

    assertEquals(0, comparator.compare(null, null));
    assertEquals(0, comparator.compare(new Object(), new Object()));

    ImmutableList<Integer> first = ImmutableList.of(0, 2, 4, 6, 8);
    ImmutableList<Integer> second = ImmutableList.of(1, 3, 5, 7, 9);

    Comparator<Object> comparator = Ordering.allEqual();
    Iterable<Integer> merged = Iterables.mergeSorted(ImmutableList.of(first, second), comparator);

    assertThat(merged).containsExactly(0, 2, 4, 6, 8, 1, 3, 5, 7, 9).inOrder();
  }