import junit.framework.TestSuite;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@code ForwardingSortedSet}.
 *
 * @author Louis Wasserman
 */
public class ForwardingSortedSetTest extends TestCase {
  static class StandardImplForwardingSortedSet<T> extends ForwardingSortedSet<T> {
    private final SortedSet<T> backingSortedSet;

    StandardImplForwardingSortedSet(SortedSet<T> backingSortedSet) {

import junit.framework.TestSuite;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@code ForwardingSortedSet}.
 *
 * @author Louis Wasserman
 */
public class ForwardingSortedSetTest extends TestCase {
  static class StandardImplForwardingSortedSet<T> extends ForwardingSortedSet<T> {
    private final SortedSet<T> backingSortedSet;

    StandardImplForwardingSortedSet(SortedSet<T> backingSortedSet) {

      return set;
    }
    return new UnmodifiableNavigableSet<>(set);
  }

  static final class UnmodifiableNavigableSet<E extends @Nullable Object>
      extends ForwardingSortedSet<E> implements NavigableSet<E>, Serializable {
    private final NavigableSet<E> delegate;
    private final SortedSet<E> unmodifiableDelegate;

    UnmodifiableNavigableSet(NavigableSet<E> delegate) {

        throw new UnsupportedOperationException();
      }
    };
  }

  private static <E extends @Nullable Object> SortedSet<E> removeOnlySortedSet(
      final SortedSet<E> set) {
    return new ForwardingSortedSet<E>() {
      @Override
      protected SortedSet<E> delegate() {
        return set;
      }

      @Override
      public boolean add(@ParametricNullness E element) {

        throw new UnsupportedOperationException();
      }
    };
  }

  private static <E extends @Nullable Object> SortedSet<E> removeOnlySortedSet(
      final SortedSet<E> set) {
    return new ForwardingSortedSet<E>() {
      @Override
      protected SortedSet<E> delegate() {
        return set;
      }

      @Override
      public boolean add(@ParametricNullness E element) {