### Question:
ConsumerGroupTopicServiceImpl extends AbstractBaseService<ConsumerGroupTopicEntity> implements CacheUpdateService, ConsumerGroupTopicService, TimerService { @Override public Map<Long, Map<String, ConsumerGroupTopicEntity>> getCache() { Map<Long, Map<String, ConsumerGroupTopicEntity>> rs = consumerGroupTopicRefMap.get(); if (rs.size() == 0) { cacheLock.lock(); try { rs = consumerGroupTopicRefMap.get(); if (rs.size() == 0) { if (first.compareAndSet(true, false)) { updateCache(); } rs = consumerGroupTopicRefMap.get(); } } finally { cacheLock.unlock(); } } return rs; }  @Override void start(); @Override void updateCache(); @Override void forceUpdateCache(); @Override Map<Long, Map<String, ConsumerGroupTopicEntity>> getCache(); @Override Map<String, ConsumerGroupTopicEntity> getGroupTopic(); @Override void deleteByConsumerGroupId(long consumerGroupId); @Override void deleteByOriginTopicName(long consumerGroupId, String originTopicName); @Override List<String> getFailTopicNames(long consumerGroupId); @Override ConsumerGroupTopicEntity getCorrespondConsumerGroupTopic(Map<String, Object> parameterMap); @Override void updateEmailByGroupName(String groupName, String alarmEmails); @PreDestroy @Override void stop(); @Override String info(); @Override String getCacheJson(); @Override Map<String, List<ConsumerGroupTopicEntity>> getTopicSubscribeMap(); @Transactional(rollbackFor = Exception.class) @Override ConsumerGroupTopicCreateResponse subscribe(ConsumerGroupTopicCreateRequest consumerGroupTopicCreateRequest); @Override ConsumerGroupTopicCreateResponse subscribe(ConsumerGroupTopicCreateRequest consumerGroupTopicCreateRequest,Map<String, ConsumerGroupEntity> consumerGroupMap); @Override ConsumerGroupTopicEntity createConsumerGroupTopic(
			ConsumerGroupTopicCreateRequest consumerGroupTopicCreateRequest); @Transactional(rollbackFor = Exception.class) @Override ConsumerGroupTopicDeleteResponse deleteConsumerGroupTopic(long consumerGroupTopicId);  }### Answer:
@Test public void getCacheTest() { assertEquals(0, consumerGroupTopicServiceImpl.getCache().size()); List<ConsumerGroupTopicEntity> consumerGroupEntities = new ArrayList<ConsumerGroupTopicEntity>(); ConsumerGroupTopicEntity consumerGroupTopicEntity = new ConsumerGroupTopicEntity(); consumerGroupEntities.add(consumerGroupTopicEntity); consumerGroupTopicEntity.setConsumerGroupName("Test"); consumerGroupTopicEntity.setTopicName("test"); consumerGroupTopicEntity.setConsumerGroupId(1); when(consumerGroupTopicRepository.getAll()).thenReturn(consumerGroupEntities); consumerGroupTopicServiceImpl.first.set(true); assertEquals(1, consumerGroupTopicServiceImpl.getCache().size()); }