I would like to start developing for iOS. Coming from an Android developing background, I know that the more types of devices you can get your hands on, the better testing will be, as all devices have wildly different specs, and what may work perfectly in your test device may not even run in another one, let alone look good.
I know that testing on the actual device is very important, as there are many limitations on what you can test on an emulator, so I've decided to get an actual device.
However, there are also tons of devices available in the iOS world! There's the iPod touch, the iPad and the iPhone, each in several different generations and configurations (8GB version vs 16GB version, WiFi version, 3G version, etc.). Not also the screen sizes, but also the aspect ratio is very different across devices, and also the included sensors.
I think that getting an application to run in varied devices should not be difficult, but is it necessary to actually test on all the device types you plan to support? Apple is not renown for its low price, and I would like to keep the starting costs as low as possible.
So, to conclude: Is it necessary/recommended to test on as many device types as you can in the iOS development world?
A small clarification: I'm specially asking if it is possible for there to be compatibility issues related to a specific device/family-of-devices that I would not be able to catch either by testing on the emulator nor a totally different device.
Generally speaking, the major differences in capabilities between testing on the simulator and testing on a device are:
Now, in my specific case, I try to test on one of each screen resolution I support and one of each major OS version I support.
This boils down to the following array of test devices:
Note that the iPad mini is the same resolution as the iPad 1st gen.
(My choices are skewed towards later iOS versions since I like to implement integration with all of Apple's snazzy optional features as they roll them out. It would probably be a more balanced assortment if one of the 6.x devices were running 5.1 instead.)
If you don't need to support 4.x, I would personally advise against it, since iTunes Connect no longer collects crash reports for it and the simulator no longer offers it. Of course, only you can decide whether you really need to or not, and if you do, focus a lot of your testing there as Xcode does not warn you if you are using APIs that were only introduced in 5.0, which will crash any device running 4.x.
Please note that there are ways to (with significant preparation) downgrade the version of iOS on a device, so if you really want to test more versions than you have devices for, you can (with a lot of effort). But you're probably better off cultivating a strong pool of beta testers for this, anyway.