I had a weird way to test it, but here goes:
Go to Play Store, click the search bar so that the keyboard comes up, and then start gesture-typing (swiping) without lifting your finger. Then go off the keyboard without lifting your finger and see if it scrolls the background. It shouldn't do that.
It should "hold" the touch -- meaning if you don't ever lift your finger, it shouldn't scroll the background or anything. It should still think you're gesture typing but just missing the keyboard really badly. The background should not scroll.
Try that.
Also, this might help? Not sure:
https://play.google.com/store/apps/details?id=multitouchpro.tests&hl=en
But, at the end of the day, if you're within your exchange period, when in doubt, just exchange it. Better to have the peace of mind even if it's a bit inconvenient.