add tests for load operations
add tests for load operations

DevExpress/DevExtreme.AspNet.Data,AlekseyMartynov/DevExtreme.AspNet.Data,AlekseyMartynov/DevExtreme.AspNet.Data,AlekseyMartynov/DevExtreme.AspNet.Data,AlekseyMartynov/DevExtreme.AspNet.Data,DevExpress/DevExtreme.AspNet.Data,DevExpress/DevExtreme.AspNet.Data,DevExpress/DevExtreme.AspNet.Data