Google Test Ad
I know - not the most Earth-shattering of WTFs. But I'll take what I can get.
-- R Flowers
It's no WTF at all if it's intentional. And you just can't tell.
I would think it was a wtf if a test ad made it out into production.
I was surprised that test.com isn't a reserved domain. Maybe this is just a sneaky marketing campaign?