private var currentTask: SerialTask = TestThreadSerialTask

  /** The coordinator task if it's waiting, and how it will resume. Guarded by [TaskRunner.lock]. */
  private var waitingCoordinatorTask: SerialTask? = null
  private var waitingCoordinatorInterrupted = false
  private var waitingCoordinatorNotified = false

  /** How many times a new task has been started. Guarded by [TaskRunner.lock]. */
  private var contextSwitchCount = 0

      "FINE: Q10000 scheduled after 100 µs: task",
      "FINE: Q10000 starting              : task",
      "FINE: Q10000 finished run in   0 µs: task",
    )
  }

  /** Inspect how many runnables have been enqueued. If none then we're truly sequential. */
  @Test fun singleQueueIsSerial() {
    redQueue.execute("task one", 100.µs) {
      log += "one:run@${taskFaker.nanoTime} parallel=${taskFaker.isParallel}"