Yep I tried the same thing. My 6S failed the Phone Doctor compass test. Compass app works fine, but compass in Phone Doctor doesn't move.FYI , there is a free app in the App Store called Phone Doctor, it checks the various components on your phone, my failed on the digital compass test, tried on 3 separate 6s+'s, all failed on the same thing.
Maybe you're using it indirectly through Google/Apple Maps. Compass has been there since the 3GS, surely Apple have nailed it by now.Do you seriously need the iPhone compass to function perfectly? I've always assumed it to be an inaccurate gimmick and have never user it, ever.