new TestStringSetGenerator() {
                  @Override
                  protected Set<String> create(String[] elements) {
                    NavigableSet<String> set = new SafeTreeSet<>(Ordering.natural().nullsFirst());
                    Collections.addAll(set, elements);
                    return set;
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {

 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class GeneralRangeTest extends TestCase {
  private static final Ordering<@Nullable Integer> ORDERING =
      Ordering.<Integer>natural().<Integer>nullsFirst();

  private static final List<@Nullable Integer> IN_ORDER_VALUES = Arrays.asList(null, 1, 2, 3, 4, 5);

  public void testCreateEmptyRangeFails() {
    for (BoundType lboundType : BoundType.values()) {

  }

  /** Decreasing integer values. A {@code null} comes before any non-null value. */
  private static final Comparator<@Nullable Integer> DECREASING_INT_COMPARATOR =
      Ordering.<Integer>natural().reverse().<Integer>nullsFirst();

  private SetMultimap<String, Integer> create() {
    return TreeMultimap.create(StringLength.COMPARATOR, DECREASING_INT_COMPARATOR);
  }

  @SuppressWarnings("unchecked")
  protected <E> NavigableSet<E> create() {
    TestSet<E> inner =
        new TestSet<>(new TreeSet<E>((Comparator<E>) Ordering.natural().nullsFirst()), null);
    NavigableSet<E> outer = Synchronized.navigableSet(inner, null);
    inner.mutex = outer;
    return outer;
  }

 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class GeneralRangeTest extends TestCase {
  private static final Ordering<@Nullable Integer> ORDERING =
      Ordering.<Integer>natural().<Integer>nullsFirst();

  private static final List<@Nullable Integer> IN_ORDER_VALUES = Arrays.asList(null, 1, 2, 3, 4, 5);

  public void testCreateEmptyRangeFails() {
    for (BoundType lboundType : BoundType.values()) {

  @SuppressWarnings("unchecked")
  protected <E> NavigableSet<E> create() {
    TestSet<E> inner =
        new TestSet<>(new TreeSet<E>((Comparator<E>) Ordering.natural().nullsFirst()), MUTEX);
    NavigableSet<E> outer = Synchronized.navigableSet(inner, MUTEX);
    return outer;
  }

  static class TestSet<E> extends SynchronizedSetTest.TestSet<E> implements NavigableSet<E> {

  }

  /** Decreasing integer values. A {@code null} comes before any non-null value. */
  private static final Comparator<@Nullable Integer> DECREASING_INT_COMPARATOR =
      Ordering.<Integer>natural().reverse().<Integer>nullsFirst();

  private SetMultimap<String, Integer> create() {
    return TreeMultimap.create(StringLength.COMPARATOR, DECREASING_INT_COMPARATOR);
  }