stopwatch.start();
    assertEquals(0, stopwatch.elapsed(NANOSECONDS));

    ticker.advance(345);
    assertEquals(345, stopwatch.elapsed(NANOSECONDS));
  }

  public void testElapsed_notRunning() {
    ticker.advance(1);
    stopwatch.start();
    ticker.advance(4);
    stopwatch.stop();
    ticker.advance(9);
    assertEquals(4, stopwatch.elapsed(NANOSECONDS));
  }