}

  @SuppressWarnings("deprecation")
  public void testUnmodifiableMultisetShortCircuit() {
    Multiset<String> mod = HashMultiset.create();
    Multiset<String> unmod = Multisets.unmodifiableMultiset(mod);
    assertNotSame(mod, unmod);
    assertSame(unmod, Multisets.unmodifiableMultiset(unmod));
    ImmutableMultiset<String> immutable = ImmutableMultiset.of("a", "a", "b", "a");

  }

  @GwtIncompatible // NavigableSet
  public void testUnmodifiableNavigableSet() {
    TreeSet<Integer> mod = Sets.newTreeSet();
    mod.add(1);
    mod.add(2);
    mod.add(3);

    NavigableSet<Integer> unmod = unmodifiableNavigableSet(mod);

    /* Unmodifiable is a view. */
    mod.add(4);
    assertTrue(unmod.contains(4));
    assertTrue(unmod.descendingSet().contains(4));