Programming Cocoa with Ruby: Create Compelling Mac Apps Using RubyCocoa (Facets of Ruby)
Brian Marick learned Ruby in 2001 because Dave Thomas and Andy Hunt, original authors of "Programming Ruby", wouldn't let him off a shuttle bus until he said he would. He's been programming in it ever since, and he's made a special effort to teach it to software testers. His previous book is "Everyday Scripting with Ruby", which began as a tutorial for those very testers. He's not a Ruby programmer by trade. He makes most of his money as a consultant in the Agile methodologies. (After getting off the shuttle bus, he was one of the authors of the "Manifesto for Agile Software Development.")