Added constraint tests for the MathDifficulty column and the ReadingDifficulty columns and deleted not needed tests (the inserting and deleting tests).
Added constraint tests for the MathDifficulty column and the ReadingDifficulty columns and deleted not needed tests (the inserting and deleting tests).

RobertMooers/ToTheRescue-,RobertMooers/ToTheRescue-,RobertMooers/ToTheRescue-