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"));

  }

  private static class SortedSetSupplier extends CountingSupplier<TreeSet<Integer>> {
    @Override
    public TreeSet<Integer> getImpl() {
      return Sets.newTreeSet(INT_COMPARATOR);
    }

    private static final long serialVersionUID = 0;
  }

  public void testNewSortedSetMultimap() {
    CountingSupplier<TreeSet<Integer>> factory = new SortedSetSupplier();

    return asList(elements).iterator();
  }

  // In GWT, java.util.TreeSet throws ClassCastException when the comparator
  // throws it, unlike JDK6.  Therefore, we accept ClassCastException as a
  // valid result thrown by java.util.TreeSet#equals.
  private static void assertNotEqualLenient(TreeSet<?> unexpected, SortedSet<?> actual) {
    try {
      assertThat(actual).isNotEqualTo(unexpected);

  }

  private static class SortedSetSupplier extends CountingSupplier<TreeSet<Integer>> {
    @Override
    public TreeSet<Integer> getImpl() {
      return Sets.newTreeSet(INT_COMPARATOR);
    }

    private static final long serialVersionUID = 0;
  }

  public void testNewSortedSetMultimap() {
    CountingSupplier<TreeSet<Integer>> factory = new SortedSetSupplier();