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Douglas McCarroll releases AS3 visual-comparison testing library

Douglas McCarroll has just released the first public incarnation of Visual FlexUnit as a Google Code project. I’m very excited about this project, partly because I think it’s going to be super useful to some people (myself included!) and partly because Douglas did a ton of great work on it during his internship this year at Allurent and it really is his baby.

I don’t want to recapitulate the whole project description, which you can read for yourself, but… what the heck is Visual FlexUnit?

It’s a version of the popular FlexUnit unit testing suite that permits visual assertions: as part of any unit test, you can verify that a particular visual component looks the way that it ought to look. The mechanics of the test involve capturing a bitmap of the component’s appearance and comparing this against a previously captured baseline, then identifying and visually highlighting the differences. This is exactly the kind of unit test that any custom UI component worth its salt ought to be subjected to, and now we finally have a tool with which to do it. Douglas’s package looks a lot like the regular FlexUnit test runner until a test fails, at which point it allows you to inspect the differences between the “correct” and “failed” appearances of a test with some clever ways of highlighting or superimposing the two views. Do you want to test your custom components by manually checking their appearance every time you change something? If you like doing that and have lots of spare time, then you won’t need this package. Otherwise, this might be something you want to check out.

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