Really well tested?
I had no choice really at first (I thought) in relying upon the information provided to me by the app when I hit "stop sleeping"...until I accidentally forgot to stop it and go in it the following night to see that it says (once I finally did stop it) that after 22hrs and 5minutes of "sleep" I was restful for a whopping 20hrs and 30 minutes. I laid in bed that nightmares less than 7hrs.
Needless to say I was disappointed. Its one of the things Apple Watch is really missing. An accurate sleep analysis.
CLOS1513 about
Sleep++