eachQueue@ for (queue in readyQueues) {
        val candidate = queue.futureTasks[0]
        val candidateDelay = maxOf(0L, candidate.nextExecuteNanoTime - now)

        when {
          // Compute the delay of the soonest-executable task.
          candidateDelay > 0L -> {
            minDelayNanos = minOf(candidateDelay, minDelayNanos)
            continue@eachQueue
          }

    taskRunner.lock.withLock {
      check(currentTask == TestThreadSerialTask)
      nanoTime = newTime
      yieldUntil(ResumePriority.AfterOtherTasks)
    }
  }

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

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