battery?

i tried startin the car this morning and the battery was drained o.O. i got it jump started and it would be fine in neuteral..but then when i put it in gear and start moving as soon as i press down the clutch it dies (not stall out but completely die) ....the alternator is almost new..couple months old and i just replaced the battery and its running fine for now but it doesn't seem like the fix for some reason..or am i just being paranoid?. should i get the alternator tested? i heard the alternator can poop out on ya randomly. thx

I would go have the alternator tested. You can have it done for free at a lot of places, so it can't hurt.