public void test_getContentTitle() {
        final Set<String> querySet = new HashSet<>();
        ViewHelper viewHelper = new ViewHelper() {
            @Override
            protected OptionalThing<Set<String>> getQuerySet() {
                return OptionalThing.of(querySet);
            }
        };
        viewHelper.init();

        querySet.add("aaa");

        final Map<String, Object> document = new HashMap<>();