KillRing { public String yank() { lastKill = false; lastYank = true; return slots[head]; } KillRing(int size);  KillRing(); void resetLastYank(); void resetLastKill(); boolean lastYank(); void add(String str); void addBackwards(String str); String yank(); String yankPop();  }
@Test public void testEmptyKillRing() { KillRing killRing = new KillRing(); assertNull(killRing.yank()); }