### Question:
TransactionalTypeAwarePluginTopicService implements TypeAwarePluginTopicService { @Override public void closeTopic(Topic topic) { topicModificationService.closeTopic(topic); } private  TransactionalTypeAwarePluginTopicService(); static TypeAwarePluginTopicService getInstance(); void setTopicFetchService(PluginTopicFetchService topicFetchService); void setTopicModificationService(PluginTopicModificationService topicModificationService); Topic get(Long id, String type); void updateTopic(Topic topic); Topic createTopic(Topic topicDto, String bodyText); void checkViewTopicPermission(Long branchId); @Override void closeTopic(Topic topic); @Override void openTopic(Topic topic); @Override Post replyToTopic(long topicId, String answerBody, long branchId);  }### Answer:
@Test public void testCloseTopic() { Topic topic = new Topic(); TransactionalTypeAwarePluginTopicService.getInstance().closeTopic(topic); verify(topicModificationService).closeTopic(topic); }