C'mon kids, drugs aren't gonna help you take tests.
I'm not being a counselor or some moral crusader, I'm all in favor of chemical performance enhancement. I'm speaking from a decade on college campuses, nailing high scores in classes when I wasn't bored, and grading your tests and listening to you whine in office hours.
You want to do well? Go in the same way you studied. Night before a big test, I stopped all work related to it by 6pm, made sure I got 8 hours of sleep, not even a glance at material in the morning (you either learned by yesterday or not). And when I went to classes, I then didn't even need to study.
If you do need to study, limit it to a productive one hour per subject per day, drugs being tea and maybe nicotine.
Coffee before a big test means you'll have to pee in the middle. If you do drink coffee first, remember it's half life is like 4 hours, you can drink it 2 hours before, no need to choke on a 20oz double-shot as you go in.
And both caffeine and your amphetamines do a great job of giving you a SENSE of productivity and clarity, not so much in reality. With your Vyvanse, you risk doing a mental carpet-combing on a single piece of your question and fail to get the whole.
Be relaxed and confident when you take tests, not jittery.