This is not as simple as it sounds on apple devices. Apple requires to register every single device you use for testing with them, register your email and apple account with them and give me access to send you the updates.
Also it has to be enough variety of devices: all with an iPhone 5 doesn't help. We need ipod 2nd, 3, and 4 generation, ipad 2, 3, 4, iPhone 4, 5, 6 and so on.
I test always myself on ipad 2, iPhone 3gs, 5s and 6 for apple. On pc I have 3 windows 8.1 pc to test, 7 different android devices and one android x86 intel chip tablet. I have the first 2 kindle devices. On windows phone I have a Lumia 520 and a 920. Every single device is different and I have to go through all of them on every update. And even then, updates go out with errors. It's just life.
Apple is specially painful to test for all the requirements to register the devices. Android is a piece of cake to send updates but each device is a complete different beast. And Windows 8.1 and Windows Phone are the easiest because they are pretty standard across all systems.