It's a great idea. Even ability to render different views and inspect them quickly by eye is really valuable when you have huge configuration space (charts for example). Adding automatic diff testing on top of that is a good idea especially when the UI style stabilizes.
Let me add another suggestion: http://www.sikuli.org/
Originally developed at MIT, now freely available and maintained as open-source lib. It offers advanced (partial) matching at the UI level.
It can be very effective. For example, WebKit has used it extensively. On the other hand, it can slow you down if your software involves rapid iteration of the UI, in which case semantic UI testing (using, eg, accessibility) may be a better solution.
Re:Mobile at Scale
by DanielRibeiro on Sunday October 27, 2013 @03:16AM
(#6621118)
I've been using another one in pure Javascript for testing WebGL Scenes: https://github.com/danielribeiro/threejs-test
Huxley is being used by Instagram for their www stack and is already open source. https://github.com/facebook/huxley
For web there is https://github.com/BBC-News/wraith , there needs to be something like this for mobile development.
So, am I still crazy for thinking screenshot diffing might be an effective way to verify builds?