I based my statement on a presentation by the folks behind Industrial XP. If you look at the http://www.industrialxp.com, you'll see "Story Testing" on the 'X'.

Ah - light dawns :-)

As I understand it storytesting (IXP people like it to be one word) is the process of elucidating acceptance tests from the client - but not actually writing them.

So the difference from vanilla XP is that IXP is making an implicit task (you need to define acceptance tests for a story in the planning game) an explicit one - which makes sense. Seems a practice that would be suited to QA people.

So it's not so much about testing stories, as it is about finding out what needs to be done to test stories (which is at the heart of XP and IXP).

However I've never been to an IXP presentation, and IXP itself seems to be in flux, so I may well be completely wrong here :-)

Keith Ray wrote a nice summary of IXPs practices that might be of interest.

Personally I can't wait for somebody to write more about their Iterative Usability practice. Since I wear a usability hat on occasion I'm spending quite a lot of time trying to integrate good UI design practices into agile development strategies - which is proving non-trivial :-)