Maybe I just go for the cheapest phone and tablet. If my game runs OK on them, they probably runs OK on the high-end devices too.
It may not be the best scenario as your game may not look good enough on those hi-end devices if you design it for low res device. During the development I even found out that one of my projects had quite opposite - the game run more smoothly on the Galaxy S (800x480) than on Galaxy SIV (1920x1080). The reason was that on the Galaxy IV game switched to hi-def assets designed for iPad retina, and it hadn't good enough fillrate to manage such high res display and hi res textures. It's just an example
During development the best way I think is to get in touch with your friends, post some facebook messages etc, to borrow some devices, or get such friend to meet for a beer and try to run your game on their devices. Or buy one. Test it as much as you can, because differences between android devices are far more unpredictable as you might imagine.
Before final Google Play release you can try out its Beta Testing option in developer console, which I would highly recommend, but it may be a bit trouble and time consuming.
Also maybe you could test some android emulator alternatives? Genymotion? My friend used it for simple apps, and found much more usefull than standard android emulator, but I hadn't test it with games.