We are developing application for mobile platforms. But it can be tested on (windows) desktop and it's obviously easier than uploading to device. However mouse is quite a bit more precise than the touch screen, so testing on desktop will indicate different things as easy/hard to use than testing on device. Is there any tool or methodology for approximating control with touch screen (and rather thick finger) on desktop?
There's no substitute for using a touch-screen for testing. If you're developing on Windows you can buy an infrared touch frame extremely cheaply (generally under $50), which is basically a frame of IR LEDs and IR sensors around a clear plastic or glass window, and a USB cable to connect it to your computer. This then sits in front of your existing display and is natively supported by Windows as a touch screen. Super, super easy.
Alternatively you can buy an external touch display (which can support anything up to 20 finger multitouch).
If you can't afford (or get your hands on) a real touch display, there are some little things you can do:
- Follow the platform's touch guidelines. Where to look for these will differ depending on the platform you're building against.
- Use an app like PhoneFinger (sadly seems to be discontinued but you can still find it around the place), which changes your mouse cursor to a big, obnoxious hand (and thus allows you to see how well your UI allows you to tap what you're trying to tap).
- If you're building an app for iOS, you could try an app like LiveView to allow you to view your PC screen via the device itself (without needing to deploy your app over and over again).
First of all why would you build an application for a mobile platform and not test it on the platform itself? Personally I would prefer real life user testing on several mobile devices.
But if you have no option to do this you could try something like the touch template developed by Steven Hoober. I haven't used it personally but it seems like an easy and straightforward solution to finding some of the problems you mention.
Image of the touch template: http://www.touchusability.com/storage/example-interference.jpeg?__SQUARESPACE_CACHEVERSION=1345404148235
Site of Steven with an explanation: http://4ourth.com/wiki/4ourth%20Mobile%20Touch%20Template (site currently not working, hopefully later on)