Multiset<String> toRetain = HashMultiset.create(asList("a", "b", "a"));
    assertFalse(Multisets.retainOccurrences(multiset, toRetain));
    assertThat(multiset).isEmpty();
  }

  public void testRemoveOccurrencesIterableEmpty() {
    Multiset<String> multiset = HashMultiset.create();
    Iterable<String> toRemove = asList("a", "b", "a");
    assertFalse(Multisets.removeOccurrences(multiset, toRemove));
    assertTrue(multiset.isEmpty());