AlarmClock alarmClock = new AlarmClock() ;
assertEquals(0, alarmClock.getCount()) ;
Pingback<?> ping1 = alarmClock.add(callback, 50) ;
Pingback<?> ping2 = alarmClock.add(callback, 100) ;
assertEquals(2, alarmClock.getCount()) ;
alarmClock.reset(ping1, 2000) ;
assertEquals(2, alarmClock.getCount()) ;
sleep(200) ; // ping2 goes off.
assertEquals(1, alarmClock.getCount()) ;
}