assertThrows(
        NullPointerException.class,
        () -> ImmutableListMultimap.copyOf((ArrayListMultimap<String, Integer>) input));
  }

  public void testToImmutableListMultimap() {
    Collector<Entry<String, Integer>, ?, ImmutableListMultimap<String, Integer>> collector =
        toImmutableListMultimap(Entry::getKey, Entry::getValue);