executor.execute(wrapper);
      }
      barrier.await(); // release the threads!
      barrier.await(); // wait for them all to complete
      assertEquals(1, task.get().intValue());
      assertEquals(1, counter.get());
    }
    executor.shutdown();
  }

  @J2ktIncompatible
  @GwtIncompatible // blocking wait
  public void testToString() throws Exception {

        executor.execute(wrapper);
      }
      barrier.await(); // release the threads!
      barrier.await(); // wait for them all to complete
      assertEquals(1, task.get().intValue());
      assertEquals(1, counter.get());
    }
    executor.shutdown();
  }

  @J2ktIncompatible
  @GwtIncompatible // blocking wait
  public void testToString() throws Exception {

    assertTrue(listenerLatch.await(5, SECONDS));
    assertTrue(task.isDone());
    assertFalse(task.isCancelled());
  }

  public void testListenerCalledOnException() throws Exception {
    throwException = true;

    // Start up the task and unblock the latch to finish the task.
    exec.execute(task);
    runLatch.await();
    taskLatch.countDown();

    assertTrue(listenerLatch.await(5, SECONDS));
    assertTrue(task.isDone());
    assertFalse(task.isCancelled());
  }

  public void testListenerCalledOnException() throws Exception {
    throwException = true;

    // Start up the task and unblock the latch to finish the task.
    exec.execute(task);
    runLatch.await();
    taskLatch.countDown();

# Concurrency and async / await { #concurrency-and-async-await }

Details about the `async def` syntax for *path operation functions* and some background about asynchronous code, concurrency, and parallelism.

## In a hurry? { #in-a-hurry }

<abbr title="too long; didn't read"><strong>TL;DR:</strong></abbr>

If you are using third party libraries that tell you to call them with `await`, like:

```Python
results = await some_library()
```

                        // WAIT #1
                        barrier.await(1, SECONDS);

                        // WAIT #2
                        barrier.await(1, SECONDS);
                        assertTrue(executor.isShutdown());
                        assertFalse(executor.isTerminated());

                        // WAIT #3
                        barrier.await(1, SECONDS);
                        return null;

                        // WAIT #1
                        barrier.await(1, SECONDS);

                        // WAIT #2
                        barrier.await(1, SECONDS);
                        assertTrue(executor.isShutdown());
                        assertFalse(executor.isTerminated());

                        // WAIT #3
                        barrier.await(1, SECONDS);
                        return null;

    Thread runner = new Thread(task);
    runner.start();
    isInterruptibleRegistered.await();
    RuntimeException expected = assertThrows(RuntimeException.class, task::interruptTask);
    assertThat(expected)
        .hasMessageThat()
        .isEqualTo("I bet you didn't think Thread.interrupt could throw");
    /*
     * We need to wait for the runner to exit. It used to be that the runner would get stuck in the

    Thread runner = new Thread(task);
    runner.start();
    isInterruptibleRegistered.await();
    RuntimeException expected = assertThrows(RuntimeException.class, task::interruptTask);
    assertThat(expected)
        .hasMessageThat()
        .isEqualTo("I bet you didn't think Thread.interrupt could throw");
    /*
     * We need to wait for the runner to exit. It used to be that the runner would get stuck in the

        for (int i = 0; i < readerThreadCount; i++) {
            final int threadIndex = i;
            readerThreads[i] = new Thread(() -> {
                try {
                    startLatch.await(); // Wait for start signal
                    long endTime = System.currentTimeMillis() + testDurationMs;
                    while (System.currentTimeMillis() < endTime) {