this.userId = userId;
    }

    /**
     * Gets the creation timestamp.
     *
     * @return the creation timestamp
     */
    public LocalDateTime getCreatedAt() {
        return createdAt;
    }

    /**
     * Sets the creation timestamp.
     *
     * @param createdAt the creation timestamp
     */

    public void test_defaultConstructor() {
        final ChatSession session = new ChatSession();
        assertNotNull(session.getSessionId());
        assertNull(session.getUserId());
        assertNotNull(session.getCreatedAt());
        assertNotNull(session.getLastAccessedAt());
        assertNotNull(session.getMessages());
        assertTrue(session.getMessages().isEmpty());
    }

    @Test

                    final StringBuilder buf = new StringBuilder();
                    buf.append('{');
                    appendJson("id", entity.getId(), buf).append(',');
                    appendJson("created-at", entity.getCreatedAt(), buf).append(',');
                    appendJson("updated-at", entity.getUpdatedAt(), buf);
                    buf.append('}');
                    buf.append('\n');
                    try {