*/
    protected abstract long readMicros();

    protected abstract void sleepMicrosUninterruptibly(long micros);

    public static SleepingStopwatch createFromSystemTimer() {
      return new SleepingStopwatch() {
        final Stopwatch stopwatch = Stopwatch.createStarted();

        @Override
        protected long readMicros() {
          return stopwatch.elapsed(MICROSECONDS);
        }

   */
  static class FakeStopwatch extends SleepingStopwatch {
    long instant = 0L;
    final List<String> events = new ArrayList<>();

    @Override
    public long readMicros() {
      return NANOSECONDS.toMicros(instant);
    }

    void sleepMillis(int millis) {
      sleepMicros("U", MILLISECONDS.toMicros(millis));
    }

    void sleepMicros(String caption, long micros) {

   */
  static class FakeStopwatch extends SleepingStopwatch {
    long instant = 0L;
    final List<String> events = new ArrayList<>();

    @Override
    public long readMicros() {
      return NANOSECONDS.toMicros(instant);
    }

    void sleepMillis(int millis) {
      sleepMicros("U", MILLISECONDS.toMicros(millis));
    }

    void sleepMicros(String caption, long micros) {