return insertionOrder;
    }
  }

  public static class ImmutableSortedSetUnhashableGenerator extends TestUnhashableSetGenerator {
    @Override
    public Set<UnhashableObject> create(UnhashableObject[] elements) {
      return ImmutableSortedSet.copyOf(elements);
    }
  }

  public static class ImmutableSetAsListGenerator extends TestStringListGenerator {
    @Override