}

  public void testMapWithIndex_arrayListSource() {
    testMapWithIndex(elems -> new ArrayList<>(elems).stream());
  }

  public void testMapWithIndex_linkedHashSetSource() {
    testMapWithIndex(elems -> new LinkedHashSet<>(elems).stream());
  }

  public void testMapWithIndex_unsizedSource() {
    testMapWithIndex(
        elems ->