Why and how to do unit testing for Cocoa (Mac) applications using OCUnit, which comes with Xcode.
I'm not an iPhone developer, so please don't ask me about testing for iPhone applications. Instead, see this blog post by my friend Colin Barrett: http://iamthewalr.us/blog/2008/11/10/ocmock-and-the-iphone/
This video is based on a presentation I gave at the December 2008 meeting of CocoaHeads in Lake Forest, California. This version is corrected and expanded from the original.