TreeSet<Integer> set = Sets.newTreeSet(SOME_COMPARATOR);
    verifySortedSetContents(set, EMPTY_COLLECTION, SOME_COMPARATOR);
  }

  public void testNewIdentityHashSet() {
    Set<Integer> set = Sets.newIdentityHashSet();
    Integer value1 = new Integer(12357);
    Integer value2 = new Integer(12357);
    assertTrue(set.add(value1));
    assertFalse(set.contains(value2));
    assertTrue(set.contains(value1));

   * way {@code IdentityHashMap} handles key lookups.
   *
   * @since 8.0
   */
  public static <E extends @Nullable Object> Set<E> newIdentityHashSet() {
    return Collections.newSetFromMap(Maps.<E, Boolean>newIdentityHashMap());
  }

  /**
   * Creates an empty {@code CopyOnWriteArraySet} instance.
   *