@Override
    protected SortedSet<String> create(String[] elements) {
      List<String> list = Lists.newArrayList(elements);
      list.add("zzz");
      return ImmutableSortedSet.copyOf(list).headSet("zzy");
    }
  }

  public static class ImmutableSortedSetTailsetGenerator extends TestStringSortedSetGenerator {
    @Override
    protected SortedSet<String> create(String[] elements) {

    @Override
    protected SortedSet<String> create(String[] elements) {
      List<String> list = Lists.newArrayList(elements);
      list.add("zzz");
      return ImmutableSortedSet.copyOf(list).headSet("zzy");
    }
  }

  public static class ImmutableSortedSetTailsetGenerator extends TestStringSortedSetGenerator {
    @Override
    protected SortedSet<String> create(String[] elements) {

			{"NBSWY3DPO5XXE3DEZZ"},
			{"NBS", "WY3", "DPO", "5XX", "E3D", "EZZ"},
			{"NBSWY3DPO5XXE3", "DEZZ"},
		}, io.ErrUnexpectedEOF},

		// Test with "ZZY" as extra input
		{"helloworld", [][]string{
			{"NBSW", "Y3DP", "O5XX", "E3DE", "ZZY"},
			{"NBSWY3DPO5XXE3DE", "ZZY"},
			{"NBSWY3DPO5XXE3DEZZY"},
			{"NBS", "WY3", "DPO", "5XX", "E3D", "EZZY"},
			{"NBSWY3DPO5XXE3", "DEZZY"},
		}, io.ErrUnexpectedEOF},