}
              awaitTaskToRun()
            } ?: return

          logger.logElapsed(task, task.queue!!) {
            var completedNormally = false
            try {
              runTask(task)
              completedNormally = true
            } finally {
              // If the task is crashing start another thread to service the queues.
              if (!completedNormally) {
                lock.withLock {

 * deterministic.
 *
 * This class ensures that at most one thread is running at a time. This is initially the JUnit test
 * thread, which yields its execution privilege while calling [runTasks], [runNextTask], or
 * [advanceUntil]. These functions don't return until the task threads are all idle.
 *
 * Task threads release their execution privilege in these ways:
 *

    blueQueue.execute("blue task", 200.µs) {
      log += "blue:run@${taskFaker.nanoTime}"
    }
    assertThat(taskFaker.executeCallCount).isEqualTo(1)

    // Nothing to do.
    taskFaker.runTasks()
    assertThat(log).isEmpty()

    // At 100.µs, the coordinator runs the red task and starts a thread for the new coordinator.
    taskFaker.advanceUntil(100.µs)
    assertThat(log).containsExactly("red:run@100000")