Titchou is correct. I would also add that Ritalin is not an amphetamine, it's a central nervous system stimulant. The usual SAMHSA drug test doesn't test for it that I know of. Adderall on the other hand is an amphetamine and would show up if you were taking a dose high enough.
I just took a pre-employment drug test today and I'm on 20mg of Adderall XR daily. I'll let you know if they say anything back.
BTW, if you are legally prescribed a medication that shows up on the test, you usually can show the pill bottle to prove you have a Rx for it. Most testing companies have a medical review officer in charge of determining if the result from the drug test is consistent the amount of the medication you're taking.
Hope that helps.