 Simply put, the test is that one must universalize the maxim (imagine that all people acted in this way) and then see if it would still be possible to perform the maxim in the world without contradiction.In "Groundwork", Kant gives the example of a person who seeks to borrow money without intending to pay it back.This is a contradiction because if it were a universal action, no person would lend money anymore as he knows that he will never be paid back.