session.setMessages(null);
        session.clearMessages();
        assertEquals(0, session.getMessageCount());
    }

    @Test
    public void test_trimHistory() {
        final ChatSession session = new ChatSession();
        for (int i = 0; i < 10; i++) {
            session.addUserMessage("Message " + i);
        }
        assertEquals(10, session.getMessageCount());