// Verify LeasePingerTimerTask has not been created.
Field field = LeasePinger.class.getDeclaredField("timerTask");
field.setAccessible(true);
TimerTask timerTask = (TimerTask) field.get(leasePinger);
assertNull(timerTask);
leasePinger.startPing();
timerTask = (TimerTask) field.get(leasePinger);
assertNotNull(timerTask);
// Verify new LeasePingerTimerTask gets created when adding new Client
// with shorter lease period.