In a recent post to his blog Alessandro Nadalin looks at a different approach to development than the usual code-first, ask questions later style, behavior-driven development, and a tool that can help you follow this method - Behat.
Although this requirement is not mandatory, BDD's power is leveraged by using stories. It basically assumes that instead of focusing on tests, we should start our development process writing down a story that a parser can translate into a test (a customer cares about features, not tests) a programmer can implement in order to verify that our software respects that story.
He talks about installing Behat via PEAR, how it can integrate with Symfony (1.4) and an example of a sample story/test file that checks a few things against a basic page. He also points out an interesting and quite useful feature of Behat - outputting the tests in a HTML-formatted result that makes for easy reading by non-developers.