The session on mock objects, mostly lead by Steve Freeman, was a bit messy but interesting. My colleague David got to show some of our code on the screen, which was scary and exciting (he felt the urge to fix some of the tests he had shown immediately after). Also, I think I finally understood the relation between mock objects and interfaces that Steve insists on.
See, I always thought that Steve was in favour in adding interfaces directly on top of concrete classes. For example, if you have a FileManager, you would also have a IFileManager.
Steve made more clear that the idea was to use interfaces to represent a role, or (more exactly) just one of the roles that a class has. That makes sense. But, to be honest, I still prefer to have a single role per class. So, no interfaces really needed.
I wish I had more time to talk with Steve. Maybe his coming book will have answers for me.