def test_message_icon(self, message_type, expected_css_class, expected_icon_class):
        """
        Verifies that a user message returns the correct CSS and icon classes.
        """
        PageLevelMessages.register_user_message(self.request, message_type, TEST_MESSAGE)
        messages = list(PageLevelMessages.user_messages(self.request))
        assert len(messages) == 1
        assert messages[0].css_class == expected_css_class
        assert messages[0].icon_class == expected_icon_class