This is interesting. This is what my vet told me too. He said many dogs live with MVD all their life without any problems. He said that I was lucky that I can prevent any longterm problems and that I have to be careful of her diet. I don'T want to do any more tests since we are on a restricted bugdet with 2 kids. But I watch out for any problems. So far, she is doing absolutely fantastic. So I won't test a non sick dog for the moment. At least, me and my vet know what to look for if she is suddenly sick.
I'm glad your test came back negative... at least now you know and you can enjoy your lovable puppy