verifySetContents(set, EMPTY_COLLECTION);
  }

  public void testNewTreeSetEmpty() {
    TreeSet<Integer> set = Sets.newTreeSet();
    verifySortedSetContents(set, EMPTY_COLLECTION, null);
  }

  public void testNewTreeSetEmptyDerived() {
    TreeSet<Derived> set = Sets.newTreeSet();
    assertTrue(set.isEmpty());
    set.add(new Derived("foo"));
    set.add(new Derived("bar"));

   * use the {@code TreeSet} constructor directly, taking advantage of <a
   * href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
   *
   * @return a new, empty {@code TreeSet}
   */
  @SuppressWarnings("rawtypes") // https://github.com/google/guava/issues/989
  public static <E extends Comparable> TreeSet<E> newTreeSet() {
    return new TreeSet<>();
  }

  /**