NO long-term studies have yet been done on ceasing menstruation altogether, and those which HAVE been done have only shown that short-term, it is likely safe ONLY so long as women menstruate at least four times per year. And to my knowledge, the tests that have been done have been done on adult, not teen women, who have special possible concerns from taking hormonal birth control just as directed.
(The sort of thing stated at that site has a pretty serious flaw, in that not menstruating due to pregnancy and not menstruating due to synthetic hormones are not the same thing.)
So, unless you have a specific health condition your GYN is trying to treat, I'd advise you get a second opinion on that practice and advice if he or she is suggesting you NEVER cease the patch.
And yes, pregnancy tests work just the same when on hormonal birth control.
A pregnancy test will still work when you're on the patch.
However, if you're using it according to your gynecologist's directions, it's safe to say you are protected from pregnancy without taking a pregnancy test. (Assuming s/he knows you intend to use the patch to prevent pregnancy, not just to regulate periods.)
If you still don't feel safe, why not back it up with condoms? This is a good idea anyway because the patch provides no protection from STD/STIs.
Copyright 1998, 2014 Heather Corinna/Scarleteen
Scarleteen.com: Providing comprehensive sex education online to teens and young adults worldwide since 1998
Information on this site is provided for educational purposes. It is not meant to and cannot substitute for advice or care provided by an in-person medical professional. The information contained herein is not meant to be used to diagnose or treat a health problem or disease, or for prescribing any medication. You should always consult your own healthcare provider if you have a health problem or medical condition.