On php|architect's A/R/T article repository today, there's a new guide written by Sebastian Bergmann - an introduction to PHPUnit.

In the last decade, PHP has developed from a niche language for adding dynamic functionality to small websites to a powerful tool making strong inroads into large-scale, business-critical Web systems. Financial institutions such as banks and insurance companies use PHP, for instance, to develop and maintain solutions for Basel II Credit Rating. Critical business logic like this needs to work correctly. But how do you ensure that it does? You test it, of course.

The tutorial takes a look at how to get started writing tests for your code and how to run those tests against your code to find problems. Sebastian also includes a few of the common misconceptions about unit testing, specifically using PHPUnit to test their apps.