assertThat(Multimaps.unmodifiableMultimap((Multimap<String, Integer>) immutable))
        .isSameInstanceAs(immutable);
  }

  @GwtIncompatible // slow (~10s)
  public void testUnmodifiableArrayListMultimap() {
    checkUnmodifiableMultimap(
        ArrayListMultimap.<@Nullable String, @Nullable Integer>create(), true);
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester