synchronizedSetMultimap(HashMultimap.<@Nullable String, @Nullable Integer>create()), false);
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testSerializingUnmodifiableSynchronizedHashMultimap() {
    Multimap<String, Integer> unmodifiable =
        prepareUnmodifiableTests(
            synchronizedSetMultimap(HashMultimap.<String, Integer>create()), false, null, null);