private static final String LS = System.lineSeparator();

    /** */
    private List<String> messages;

    public ModelValidationResult() {
        messages = new ArrayList<>();
    }

    public int getMessageCount() {
        return messages.size();
    }

    public String getMessage(int i) {
        return messages.get(i);
    }

    public List<String> getMessages() {

        this.lastAccessedAt = LocalDateTime.now();
    }

    /**
     * Returns the number of messages in this session.
     *
     * @return the message count
     */
    public int getMessageCount() {
        synchronized (messagesLock) {
            return messages != null ? messages.size() : 0;
        }
    }

    /**

        final ChatSession session = new ChatSession();
        assertEquals(0, session.getMessageCount());

        session.addUserMessage("First");
        assertEquals(1, session.getMessageCount());

        session.addAssistantMessage("Second");
        assertEquals(2, session.getMessageCount());
    }

    @Test
    public void test_getMessageCountWithNullMessages() {