delete useless code
add get_item_by_id_test
success get_item_by_id_test
add add_item_test
success in add_item_test
update ItemServiceTest
add edit_item_test
success in edit_item_test
add remove_item_test
update remove_item_test
success in remove_item_test
new CategoryServiceTest Class
update CategoryServiceTest
new CategoryService Class
new CategoryDao class
update CategoryDao
add @Autowired to ItemService & CategoryService
add setter to CategoryService
add add_category_test
success in add_category_test