MockCallback callback = new MockCallback("foo");
    addCallback(f, callback, directExecutor());
    f.set("foo");
  }

  public void testExecutorSuccess() {
    CountingSameThreadExecutor ex = new CountingSameThreadExecutor();
    SettableFuture<String> f = SettableFuture.create();
    MockCallback callback = new MockCallback("foo");
    Futures.addCallback(f, callback, ex);
    f.set("foo");

    boolean ran = false;
    @Nullable Callback callback = null;

    public SimpleTearDown() {}

    public SimpleTearDown(Callback callback) {
      this.callback = callback;
    }

    @Override
    public void tearDown() throws Exception {
      if (callback != null) {
        callback.run();
      }
      ran = true;
    }
  }

      Class<Throwable> exceptionType,
      Function<? super Throwable, ? extends V> fallback,
      Executor executor) {
    return (FluentFuture<V>) Futures.catching(this, exceptionType, fallback, executor);
  }

  public final FluentFuture<V> catchingAsync(
      Class<Throwable> exceptionType,
      AsyncFunction<? super Throwable, ? extends V> fallback,
      Executor executor) {

 * and performant but introduces some testing difficulties. This test exercises the two fallback
 * strategies.
 *
 * <ul>
 *   <li>SafeAtomicHelper: uses Atomic FieldsUpdaters to implement synchronization
 *   <li>SynchronizedHelper: uses {@code synchronized} blocks for synchronization
 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AggregateFutureState} (and all of

      queue.dispatch();
    } finally {
      logger.removeHandler(logHandler);
    }

    assertEquals(1, logHandler.getStoredLogRecords().size());
    assertEquals(
        "Exception while executing callback: MyListener custom-label",
        logHandler.getStoredLogRecords().get(0).getMessage());
  }

  public void testEnqueueAndDispatch_multithreaded() throws InterruptedException {
    Object listener = new Object();

    boolean ran = false;
    @Nullable Callback callback = null;

    public SimpleTearDown() {}

    public SimpleTearDown(Callback callback) {
      this.callback = callback;
    }

    @Override
    public void tearDown() throws Exception {
      if (callback != null) {
        callback.run();
      }
      ran = true;
    }
  }

  }

  /**
   * Streams lines from a URL, stopping when our callback returns false, or we have read all of the
   * lines.
   *
   * @param url the URL to read from
   * @param charset the charset used to decode the input stream; see {@link Charsets} for helpful
   *     predefined constants
   * @param callback the LineProcessor to use to handle the lines
   * @return the output of processing the lines

    listener = new MockFutureListener(resultFuture);
  }

  public void testFutureGetBeforeCallback() throws Exception {
    // Verify that get throws a timeout exception before the callback is called.
    assertThrows(TimeoutException.class, () -> resultFuture.get(1L, TimeUnit.MILLISECONDS));
  }

  public void testFutureGetThrowsWrappedException() throws Exception {
    inputFuture.setException(EXCEPTION);

    // instance.  It is always safe to return the same instance because
    // javascript is single-threaded, and only used by blocks that doesn't
    // involve async callbacks.
    return CHAR_BUFFER;
  }

  private Platform() {}

    this.constructions = constructions;
    this.constructionAsymptotics = constructionAsymptotics;
    this.queries = queries;
  }

  /**
   * A Comparable wrapper around a String which executes callbacks on calls to hashCode, equals, and
   * compareTo.
   */
  private static class CountsHashCodeAndEquals implements Comparable<CountsHashCodeAndEquals> {
    private final String delegateString;