boolean changed = Iterators.addAll(alreadyThere, freshlyAdded.iterator());

    assertThat(alreadyThere).containsExactly("already", "there", "freshly", "added");
    assertTrue(changed);
  }

  public void testAddAllToSet() {
    Set<String> alreadyThere = new LinkedHashSet<>(asList("already", "there"));
    List<String> oneMore = Lists.newArrayList("there");

    boolean changed = Iterators.addAll(alreadyThere, oneMore.iterator());