Map<IntegerDiv10, String> copy = ImmutableMap.copyOf(original);
    assertTrue(original.containsKey(twelve));
    assertFalse(copy.containsKey(twelve));
  }

  public void testBuilderReverseOrder() {
    ImmutableSortedMap<String, Integer> map =
        ImmutableSortedMap.<String, Integer>reverseOrder()
            .put("one", 1)
            .put("two", 2)
            .put("three", 3)