return failFastResponse!!
    }

    val result = responseQueue.take()

    // If take() returned because we're shutting down, then enqueue another dead letter so that any
    // other threads waiting on take() will also return.
    if (result == DEAD_LETTER) responseQueue.add(DEAD_LETTER)

    return result
  }

  public override fun peek(): MockResponse = responseQueue.peek() ?: failFastResponse ?: super.peek()

    peer.acceptFrame() // ACK SETTINGS
    peer.acceptFrame() // PING
    peer.sendFrame().ping(true, Http2Connection.AWAIT_PING, 0)
    peer.acceptFrame() // SYN_STREAM
    peer.sendFrame().headers(false, 3, headerEntries("a", "android"))
    peer.acceptFrame() // PING
    peer.sendFrame().ping(true, Http2Connection.AWAIT_PING, 0)
    peer.acceptFrame() // DATA
    peer.acceptFrame() // RST_STREAM
    peer.play()

Blocking APIs may be inefficient because you hold a thread idle while waiting on the network. Threads are expensive because they have both a memory overhead and a context-switching overhead.

#### Framed protocols

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

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

    // Queue a task to interrupt the waiting coordinator.
    serialTaskQueue +=
      object : SerialTask {
        override fun start() {

    if (cancel) {
      cancel = false
      eventSource.cancel()
    }
  }

  private fun nextEvent(): Any =
    events.poll(10, TimeUnit.SECONDS)
      ?: throw AssertionError("Timed out waiting for event.")

  fun assertExhausted() {
    assertThat(events).isEmpty()
  }

  fun assertEvent(
    id: String?,
    type: String?,
    data: String,
  ) {

        // A already finished
        assertEquals(0, activeDependenciesC.size());

        List<MavenProject> activeDependenciesX = graph.getActiveDependencies(ProjectDependencyGraphStub.X);
        // waiting for C
        assertEquals(1, activeDependenciesX.size());
    }

 * ordinary tests.
 *
 * <p>Failure of the expected event to occur within an implementation-defined "reasonable" time
 * period or an interrupt while waiting for the expected event will result in a {@link
 * RuntimeException}.
 *
 * <p>Here's an example that tests a {@code finalize} method:
 *
 * {@snippet :
 * final CountDownLatch latch = new CountDownLatch(1);

    <interactiveMode>true</interactiveMode>
    ]]></configuration>
      <description>
        <![CDATA[
      If false, flags the system to skip prompting the user for any information, or holding up the build
      waiting for any input.

      NOTE: It's also possible to switch to batch (i.e. non-interactive) mode using the '-B' command-line option.
    ]]></description>
    </expression>
  </expressions>

    startsFirst.start()
    val endsFirst = buildRequestThread(secondRequest, secondResponseCode)
    endsFirst.start()
    endsFirst.join()
    // First response is still waiting.
    assertThat(firstResponseCode.get()).isEqualTo(0)
    // Second response is done.
    assertThat(secondResponseCode.get()).isEqualTo(200)
    latch.countDown()
    startsFirst.join()
    // And now it's done!

      }
      val nowMillis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime())
      if (nowMillis >= timeoutMillis) break
      (this as Object).wait(timeoutMillis - nowMillis)
    }

    throw AssertionError("Timed out waiting for response to $url")
  }

  companion object {
    val TIMEOUT_MILLIS = TimeUnit.SECONDS.toMillis(10)
  }