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

    void sleepMicros(String caption, long micros) {
      instant += MICROSECONDS.toNanos(micros);
      events.add(caption + String.format(Locale.ROOT, "%3.2f", (micros / 1000000.0)));
    }

    @Override
    protected void sleepMicrosUninterruptibly(long micros) {
      sleepMicros("R", micros);
    }

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

    void sleepMicros(String caption, long micros) {
      instant += MICROSECONDS.toNanos(micros);
      events.add(caption + String.format(Locale.ROOT, "%3.2f", (micros / 1000000.0)));
    }

    @Override
    protected void sleepMicrosUninterruptibly(long micros) {
      sleepMicros("R", micros);
    }