/** Returns a new started daemon Thread running the given runnable. */
  final Thread newStartedThread(Runnable runnable) {
    Thread t = new Thread(runnable);
    t.setDaemon(true);
    t.start();
    return t;
  }

  /**
   * Waits for the specified time (in milliseconds) for the thread to terminate (using {@link
   * Thread#join(long)}), else interrupts the thread (in the hope that it may terminate later) and

public class DeferredTest {
    @Test
    public void test_doneBeforeResolve() throws Exception {
        final Deferred<SuggestResponse> deferred = new Deferred<>();

        Thread th = new Thread(() -> {
            try {
                Thread.sleep(100);
            } catch (InterruptedException ignore) {}
            deferred.resolve(new SuggestResponse("", 0, Collections.emptyList(), 0, null));
        });
        th.start();

    assertTrue(Thread.holdsLock(mutex));
    return super.add(o);
  }

  @Override
  public boolean addAll(Collection<? extends E> c) {
    assertTrue(Thread.holdsLock(mutex));
    return super.addAll(c);
  }

  @Override
  public void clear() {
    assertTrue(Thread.holdsLock(mutex));
    super.clear();
  }

  @Override
  public boolean contains(@Nullable Object o) {
    assertTrue(Thread.holdsLock(mutex));

    assertTrue(Thread.holdsLock(mutex));
    return super.add(o);
  }

  @Override
  public boolean addAll(Collection<? extends E> c) {
    assertTrue(Thread.holdsLock(mutex));
    return super.addAll(c);
  }

  @Override
  public void clear() {
    assertTrue(Thread.holdsLock(mutex));
    super.clear();
  }

  @Override
  public boolean contains(@Nullable Object o) {
    assertTrue(Thread.holdsLock(mutex));

So we have a dedicated thread for every socket that just reads frames and dispatches them.

The reader thread must never run application-layer code. Otherwise one slow stream can hold up the entire connection.

    @RepeatedTest(10)
    @DisplayName("Test thread safety")
    void testThreadSafety() throws InterruptedException {
        SimpleCircuitBreaker breaker = new SimpleCircuitBreaker("concurrent", 5, 3, 100);
        AtomicInteger successCount = new AtomicInteger(0);
        AtomicInteger failureCount = new AtomicInteger(0);

        // Create multiple threads
        Thread[] threads = new Thread[10];

            monitor.leave();
          }
        });
    awaitUninterruptibly(enteredLatch);
  }

  @CanIgnoreReturnValue
  static Thread startThread(Runnable runnable) {
    Thread thread = new Thread(runnable);
    thread.setDaemon(true);
    thread.start();
    return thread;
  }

  /**
   * Generates a test case verifying that calling any enterXxx, tryEnterXxx, or waitForXxx method

    }

    @Override
    public int size() {
      assertTrue(Thread.holdsLock(mutex));
      return super.size();
    }

    @Override
    public boolean isEmpty() {
      assertTrue(Thread.holdsLock(mutex));
      return super.isEmpty();
    }

    @Override
    public @Nullable V remove(Object object) {
      assertTrue(Thread.holdsLock(mutex));
      return super.remove(object);
    }

    @Override

      Thread.currentThread().interrupt();
      // better than `end > System.nanoTime()` because `System.nanoTime()` could wrap around
      return end - System.nanoTime() > 0;
    }
  }

  /** Invokes {@code toJoin.}{@link Thread#join() join()} uninterruptibly. */
  @J2ktIncompatible
  @GwtIncompatible // concurrency
  public static void joinUninterruptibly(Thread toJoin) {
    boolean interrupted = false;
    try {

  }

  @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait.
  static void awaitWaiting(Thread t) {
    while (true) {
      Thread.State state = t.getState();
      switch (state) {
        case RUNNABLE:
        case BLOCKED:
          Thread.yield();
          break;
        case WAITING:
          return;
        default: