public void testSymmetricDifference_minSize() {
    assertMinSize(symmetricDifference(emptySet(), emptySet()), 0);
    assertMinSize(symmetricDifference(setSize(2), setSize(3)), 1);
    assertMinSize(symmetricDifference(setSize(3), setSize(2)), 1);
    assertMinSize(symmetricDifference(setSizeRange(10, 20), setSizeRange(1, 2)), 8);
    assertMinSize(symmetricDifference(setSizeRange(1, 2), setSizeRange(10, 20)), 8);

   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   *
   * @since 3.0
   */
  public static <E extends @Nullable Object> SetView<E> symmetricDifference(
      Set<? extends E> set1, Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override