When it comes to testing mobile devices one question will become relevant sooner or later:

What devices do I need to test? What configuration (OS, browser versions) do I need to test?

One good approach is to ask marketing, business development or whoever is responsible what the target market is (or what they promised the customer). Certainly don't trust the your device pool to be representative. Another good place is to look at statistics on current device distribution. I'd like to recommend two sources:

A weekly updated statistic of iOS device usage: https://david-smith.org/iosversionstats/

Googles Android OS distribution: http://developer.android.com/about/dashboards/index.html