Why did my 1993 mazda protege die while driving?

i have a 1993 mazda protege automatic transmission. i've been having problems with my battery draining, so i bought a new battery and brought my alternator to O'Reilly auto parts and got it checked and they say it passed all tests. my friend who has a shop took his volt meter and tested it while it was in my car and it ran 12.2V, so i bought a new alternator and put that in my car and it also read 12.2V. so i was driving home last night and my lights became dimm and it seemed my car didn't want to go into the next gear while i was driving 70mph so it had a high rpms. a couple minutes later my interior and exterior lights were really dimm and my car slowly slowed down and then just died. i had my friend try jump start my car and my car wouldn't start so i had it towed to his shop. what do you think is the problem? how come it won't start when i'm trying to jump it? will the car start with a shot alternator?