We had a parvo test done on our pup, unfortunately he was quite sick when he arrived (but that's another story). The test itself only took about five minutes, we waited in the consult room while our vet ran it. I'm not sure how much it costs, as we handed so much money over to our vet at the time for an array of things!
I would do it, even if it's just to put your mind at ease - it did for us.