* good reference implementation. As with {@code IteratorTester}, a concrete subclass must provide
 * target iterators on demand. It also requires three additional constructor parameters: {@code
 * elementsToInsert}, the elements to be passed to {@code set()} and {@code add()} calls; {@code
 * features}, the features supported by the iterator; and {@code expectedElements}, the elements the
 * iterator should return in order.
 *

 * good reference implementation. As with {@code IteratorTester}, a concrete subclass must provide
 * target iterators on demand. It also requires three additional constructor parameters: {@code
 * elementsToInsert}, the elements to be passed to {@code set()} and {@code add()} calls; {@code
 * features}, the features supported by the iterator; and {@code expectedElements}, the elements the
 * iterator should return in order.
 *

   * Object#equals} and {@link Object#hashCode}, and its construction requires a parameter of {@code
   * type}, the distinct values of {@code type} can be passed as parameters to create {@code Foo}
   * instances that are unequal.
   *
   * <p>Calling {@code setDistinctValues(type, v1, v2)} also sets the default value for {@code type}
   * that's used for {@link #testNulls}.
   *

   * IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
   * fromElement}. However, this method doesn't throw an exception in that situation, but instead
   * keeps the original {@code fromElement}. Similarly, this method keeps the original {@code
   * toElement}, instead of throwing an exception, if passed a {@code toElement} greater than an
   * earlier {@code toElement}.
   */

   * cases.
   */
  protected abstract ListenableFuture<T> buildChainingFuture(ListenableFuture<Integer> inputFuture);

  /**
   * Override to return the result when VALID_INPUT_DATA is passed in to the chaining
   * listenableFuture
   */
  protected abstract T getSuccessfulResult();

       * another thread did it for us.
       */
      seenExceptionsLocal = requireNonNull(seenExceptions);
    }
    return seenExceptionsLocal;
  }

  /** Populates {@code seen} with the exception that was passed to {@code setException}. */
  abstract void addInitialException(Set<Throwable> seen);

  final int decrementRemainingAndGet() {
    return ATOMIC_HELPER.decrementAndGetRemainingCount(this);
  }

   */
  public interface ClosingCallable<V extends @Nullable Object> {
    /**
     * Computes a result, or throws an exception if unable to do so.
     *
     * <p>Any objects that are passed to {@link DeferredCloser#eventuallyClose(Object, Executor)
     * closer.eventuallyClose()} will be closed when the {@link ClosingFuture} pipeline is done (but

   *       {@link Object#equals(Object)}.
   *   <li>{@code false} in all other situations.
   * </ul>
   *
   * <p>This assumes that any non-null objects passed to this function conform to the {@code
   * equals()} contract.
   *
   * <p><b>Java 7+ users:</b> This method should be treated as deprecated; use {@link
   * java.util.Objects#equals} instead.
   */

    this.testsEquals = true;
    return this;
  }

  /**
   * Tests that the forwarding wrapper returned by {@code wrapperFunction} properly forwards method
   * calls with parameters passed as is, return value returned as is, and exceptions propagated as
   * is.
   */
  public <T> void testForwarding(
      Class<T> interfaceType, Function<? super T, ? extends T> wrapperFunction) {

    this.testsEquals = true;
    return this;
  }

  /**
   * Tests that the forwarding wrapper returned by {@code wrapperFunction} properly forwards method
   * calls with parameters passed as is, return value returned as is, and exceptions propagated as
   * is.
   */
  public <T> void testForwarding(
      Class<T> interfaceType, Function<? super T, ? extends T> wrapperFunction) {