responseDequeuedLatches[responseIndex].countDown()
      requestCanceledLatches[responseIndex].await()
      responseIndex++
      return response
    }
  }

  /** Make a call and canceling it as soon as it's accepted by the server.  */
  private fun callAndCancel(
    expectedSequenceNumber: Int,
    responseDequeuedLatch: CountDownLatch?,
    requestCanceledLatch: CountDownLatch?,
  ) {