In this session, I'll explain the benefits of practicing test driven development and a variation called behavior driven development.
There's going to be a short introduction to the concept of optimal experience called "flow" and why the process of writing verifiable requirements in the form of tests first means nothing else than optimizing development for flow experiences.
You'll also learn how to write your modules "outside-in" utilizing a BDD framework for PHP called Behat (http://behat.org). Right now, I'm working on a solid integration of Behat with Drupal Simpletest which I hope to release prior to Drupalcity and provide you with all the tools necessary to practice real BDD with Drupal.
UPDATE: I've released a preview of the upcoming behat integration with Drupal. Please visit http://bdd.alexo.it for more information on the project. Contributions welcome!