On his blog today, Jani Hartikainen has posted the third part of his series looking at unit testing in PHP applications.

Now that you know what unit testing is and how to write and run tests, it's time to look at writing tests in more depth. Today we'll take an example class and write tests for it. We'll also introduce some common testing methodologies.

He creates the sample test (this one), makes a sample testing class for it and looks at the difference between testing code and testing behavior.