Kevin Skoglund is (according to his site) a web developer and instructor specializing in Ruby on Rails, PHP, SQL, HTML, and CSS. He is also running a series of articles on ‘Testing in Rails’. Currently he has the introduction and the first 5 of X parts posted. This search will give you all the articles in the series though I suggest you just subscribe to his rss as there are other good things that come out from him too it seems.

For those too lazy to click one of the above links, here are direct links to the articles out at time of writing.

• Introduction
• Unit Testing in Ruby
• Unit Testing Ruby Classes (con’t)
• Unit Testing in Rails
• Unit Testing using ActiveRecord Models
• Fixtures
• ActiveRecord Relationships
• Validations
• Attributes and Callbacks
• Running Unit Tests

(found via Mike Gunderloy)