}

    // Test thread safety
    public void test_threadSafety() {
        // Test that the provider returns the same instances in multi-threaded environment
        final int threadCount = 10;
        final Thread[] threads = new Thread[threadCount];
        final InvertibleCryptographer[] invertibles = new InvertibleCryptographer[threadCount];

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.

    assertFalse(future.isDone());
    assertFalse(future.isCancelled());

    CountDownLatch successLatch = new CountDownLatch(1);

    // Run cancellation in a separate thread as an extra thread-safety test.
    new Thread(
            () -> {
              assertThrows(CancellationException.class, future::get);
              successLatch.countDown();
            })
        .start();

      }
    }
  }

  private static class Interrupter implements Runnable {
    final Thread threadToInterrupt;

    Interrupter(Thread threadToInterrupt) {
      this.threadToInterrupt = threadToInterrupt;
    }

    @Override
    public void run() {
      try {
        Thread.sleep(100);
      } catch (InterruptedException e) {
        throw new AssertionError();
      } finally {

    }
  }

  /** Confirm all tasks have completed. Used by the test thread only. */
  fun assertNoMoreTasks() {
    taskRunner.assertLockNotHeld()

    taskRunner.withLock {
      assertThat(activeThreads).isEqualTo(0)
    }
  }

  /** Unblock a waiting task thread. Used by the test thread only. */
  fun interruptCoordinatorThread() {
    taskRunner.assertLockNotHeld()

        // Trip circuit
        circuitBreaker.trip();
        Thread.sleep(100);

        long afterTripTime = circuitBreaker.getTimeSinceLastStateChange();
        assertTrue(afterTripTime >= 100, "Time should have advanced");
        assertTrue(afterTripTime < 200, "Time should be reasonable");

        // Reset circuit
        circuitBreaker.reset();
        Thread.sleep(50);

    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));

        // Start a thread to set crawler running after a delay
        Thread thread = new Thread(() -> {
            try {
                Thread.sleep(100);
                helper.setCrawlerRunning(true);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        });
        thread.start();

  }

  @JvmStatic
  fun threadFactory(name: String): ThreadFactory =
    object : ThreadFactory {
      private var nextId = 1

      override fun newThread(runnable: Runnable): Thread = Thread(runnable, "$name-${nextId++}")
    }
}

fun getEnv(name: String) = System.getenv(name)

val SYSTEM_FILE_SYSTEM = FileSystem.SYSTEM