Best practices for iPhone apps on multiple OS versions

Question

I'm developing an app that uses iOS4 features (like MFMessageComposeViewController), but I want to support iOS 3.1.x as well. I know how to do that in code and build settings, but it's getting hard to find devices to test on--I've upgraded my phone and so have most of my friends. And the simulator with XCode 3.2 doesn't support simulating 3.1 as far as I can tell.

When my apps are raking in money hand over fist, of course I'll invest in multiple devices to test different OS and hardware, but I'm wondering what people do when they're starting out and resources are limited. For example, to test an SMS-capable device with 3.1.x, I'd need not only a spare device, but I'd have to pay for a phone service plan as well.

A couple of things I've considered in the meantime:

• Install an older version of XCode and use that simulator for 3.1 testing
• Buy a used iPod touch and install OS 3.1 (but couldn't test SMS/GPS)

Other ideas? I'd love to hear what other people are doing.

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Answer 1

We have a couple of devices at our startup company, and also have very old iPods. Perhaps you can get some for very little second hand?

OffTopic: I think supporting versions old of an OS when a free update is available shouldn't be done for too long. People need a bit of "help" updating. Must admit that iOS 4 might be an exception though, my iPod doesn't live for long with it installed. :(

Answer 2

What I do is keep one of each model of iPhone and iPod touch and install the latest version of the OS that runs on it. So I have iPhone 2G and iPod touch 1G with OS 3.1.3; iPhone 3GS, iPhone 4, and iPod touch 2G with OS 4.0; and a WiFi iPad with OS 3.2. Only one of the phones has cell phone service.

As for my builds, I build with SDK 4.0 and set OS 3.1.3 as the earliest target. If you claim to support a certain OS, you must have tested on the device with that OS.