boolean isParallel = false;
    int characteristics = Spliterator.ORDERED | Spliterator.SIZED | Spliterator.NONNULL;
    long estimatedSize = 0L;
    ImmutableList.Builder<Spliterator<? extends T>> splitrsBuilder =
        new ImmutableList.Builder<>(streams.length);
    for (Stream<? extends T> stream : streams) {
      isParallel |= stream.isParallel();

      log += "one:run@${taskFaker.nanoTime} parallel=${taskFaker.isParallel}"
    }

    redQueue.execute("task two", 100.µs) {
      log += "two:run@${taskFaker.nanoTime} parallel=${taskFaker.isParallel}"
    }

    redQueue.execute("task three", 100.µs) {
      log += "three:run@${taskFaker.nanoTime} parallel=${taskFaker.isParallel}"
    }

    taskFaker.advanceUntil(0.µs)
    assertThat(log).isEmpty()

  private val tasksExecutor = Executors.newCachedThreadPool(threadFactory("TaskFaker"))

  /**
   * True if this task faker has ever had multiple tasks scheduled to run concurrently. Guarded by
   * `this`.
   */
  var isParallel = false

  /** Number of calls to [TaskRunner.Backend.execute]. Guarded by `this`. */
  var executeCallCount = 0

  /** Guarded by [taskRunner]. */
  var nanoTime = 0L
    private set