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

  public void testToImmutableSetMultimap() {
    Collector<Entry<String, Integer>, ?, ImmutableSetMultimap<String, Integer>> collector =
        toImmutableSetMultimap(Entry::getKey, Entry::getValue);

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

  // TODO(b/172823566): Use mainline testToImmutableSetMultimap once CollectorTester is usable.
  public void testToImmutableSetMultimap_java7_combine() {
    ImmutableSetMultimap.Builder<String, Integer> zis =