The Scottish Government say the tests will help them gather important data for schools. But opponents say the tests cause unnecessary stress for some youngsters.
But what are the test questions actually like?
Introduced to pupils by a character named Alison, pupils are given multiple choice questions to answer.
The quiz adapts itself to offer simpler questions to pupils who are struggling and trickier questions for those performing well.
The teacher is given a detailed report on how each pupil performed.