assertThat(exception.cause)
      .isNotNull()
      .matchesPredicate { it is InterruptedException || it is RejectedExecutionException }
    assertThat(clientTestRule.takeUncaughtException())
      .matchesPredicate { it == null || it is RejectedExecutionException }
  }

  private fun sleep(delayMillis: Int) {
    try {
      Thread.sleep(delayMillis.toLong())

    }
  }

  @Synchronized private fun initUncaughtException(throwable: Throwable) {
    if (uncaughtException == null) {
      uncaughtException = throwable
    }
  }

  @Synchronized fun takeUncaughtException(): Throwable? =
    uncaughtException
      .also { uncaughtException = null }

  fun ensureAllConnectionsReleased() {
    testClient?.let {
      val connectionPool = it.connectionPool