He therefore put his geography-book under his pillow, because he had heard that was a very good thing to do when one wants to learn one's lesson; but one cannot, however, rely upon it entirely.
Also, when you're revising for tests, it's doubly important that you study actively, like if you're just passively going through your notes and textbooks, you're wasting a lot of precious time.
Set a timer to simulate the test's time limit, and quiz yourself without having access to your textbook, notes, or any other materials that you won't have during the test.