@Test
    public void topicsTest() {
        Content banana = new Content();
        banana.setContent("banana");
        
        Content apple = new Content();
        apple.setContent("apple");
        
        Content orange = new Content();
        orange.setContent("orange");
        
        speaker.addContent("Fruit", orange);
        speaker.addContent("Fruit", apple);
        speaker.addContent("Fruit", banana);
        
        Content goat = new Content();
        goat.setContent("goat");
        
        Content dog = new Content();
        dog.setContent("dog");
        
        speaker.addContent("Animals", goat);
        speaker.addContent("Animals", dog);
        
        HashMap<String, List<Content>> map = speaker.getTopics();
        for (List<Content> topic : map.values()) {
            for (Content content : topic) {
                System.out.println(content.getContent());
            }
        }
        
        //print out the keys
        System.out.println("=== keys ===");
        for (String key : map.keySet()) {
            System.out.println(key);
        }
    }