This might not be the answer to your question but just from my
experience I would like to share that the best practice would be to
get as much real devices as you can. Obviously devices costs but
that's how you can be sure about it.
As also suggested above you can give a try to bluestacks as would get the wifi
and system tools easily connected to you i.e. better in performance then the native emulator provided by Android.
With that the best thing would be to get your app tested on some devices of different Classes
.
By classes above I mean ,
- Different resolutions
- Screen sizes
- Android versions
Or, these days some testing organizations are also there who have got a number of devices and they do the testing for you on real devices hence you won't need to pay for a device , its just a suggestion or you can suggest to someone.
--Edit--
I recently have gone through Genymotion and I have found it better then any other emulators,
http://www.genymotion.com/
--Update - Nov 2020--
Bluestacks has improved a lot lately and is free to use for most of the features. I have tried testing multiple instances of the app and it worked like charm by emulating two phones, sharing data via links etc.