fun runNextTask() {
    taskRunner.assertLockNotHeld()

    taskRunner.withLock {
      val contextSwitchCountBefore = contextSwitchCount
      yieldUntil(ResumePriority.BeforeOtherTasks) {
        contextSwitchCount > contextSwitchCountBefore
      }
    }
  }

  /** Sleep until [durationNanos] elapses. For use by the task threads. */
  fun sleep(durationNanos: Long) {