final ChatMessage message = new ChatMessage();
        final ChatSource source = new ChatSource();
        source.setIndex(1);
        source.setTitle("Test Document");

        message.addSource(source);

        assertEquals(1, message.getSources().size());
        assertEquals("Test Document", message.getSources().get(0).getTitle());
    }

    @Test
    public void test_addSourceWithNullSources() {