* TODO: improve this and other implementations and move out of this framework
   * for wider use
   *
   * TODO: could we incorporate the overriding logic from AbstractListTester, by
   * examining whether the features include KNOWN_ORDER?
   */
  protected void expectContents(Collection<E> expected) {
    Helpers.assertEqualIgnoringOrder(expected, actualContents());
  }

  protected void expectUnchanged() {

   * TODO: improve this and other implementations and move out of this framework
   * for wider use
   *
   * TODO: could we incorporate the overriding logic from AbstractListTester, by
   * examining whether the features include KNOWN_ORDER?
   */
  protected void expectContents(Collection<E> expected) {
    Helpers.assertEqualIgnoringOrder(expected, actualContents());
  }

  protected void expectUnchanged() {