fixed bug of duplicated resources in prefetch items
wrote test to compare element sizes in item1
fixed test resource file that was outdated and causing warnings (category stu3 vs r4)
please note that order of item1, item2... of the prefetch JSON is not kept but modified items are currently appended at the end of the list since the JSON Object is unordered, e.g. item2-item3-item4-item1