BubbleCache { public Optional<BubbleMessage> getBubble(String eventId){ return Optional.ofNullable(this.cache.get(eventId)); }  void addBubble(String key,BubbleMessage bubbleMessage); Optional<BubbleMessage> getBubble(String eventId);  }
@Test public void testGetBubbleWhenNotExist() { final String eventId = "eventId"; final Optional<BubbleMessage> result = bubbleCacheUnderTest.getBubble(eventId); assertFalse(result.isPresent()); }