@Test
public void fixTopicShouldChangeAndUpdateAndNotifyNewTopic() throws CommandException {

    topic.changeTopic(new Topic("Topic", "Peter", 12345678));
    parser.fixTopic(" new topic"); // Includes whitespace from "/topic new topic"
    verify(controller).changeTopic("new topic");
    verify(messageController).showSystemMessage("You changed the topic to: new topic");
    verify(userInterface).showTopic();
}