Chris Hartjes has a post on his site sharing a video from a presentation he gave about "metatesting" to a local PHP user group:

Yesterday I gave a short talk at GPUG about a topic I've dubbed "metatesting". Borrowing the phrase from a children's card game I wanted to talk about the state of testing and associated tools.

You can watch the presentation through the in-page video player including both the slides and Chris' presentation of them. In it he talks about mature testing tools (and extending them rather than creating new ones), open source projects and their tests or lack thereof, how testing reduces the cost of bugfixing and much more. Check out the full presentation for some great tips and updates on where software (and PHP) testing is today.