I always find that the common user is the best approach to testing and finding bugs. I have developed many web and mobile apps and for the last 8, I gave the app away to 40 people. If you give the app for free, people will be glad to test it and they will find more bugs than any technical QA testing person since QA techs think technically and not the way the common end user would.

I have found that the common end user is most rock solid approach and it is free.

Bruce