Stefil might be the test framework I'm looking for: powered by CLOS and integrating with Slime. Thanks for sharing!
The swank integration is a bit outdated though: function inspect-for-emacs has been renamed into emacs-inspect, and its second argument, inspector, was dropped. I've attached a patch that fixes this (and probably breaks things in your custom slime branch). Also there seems no reason for inspector-result to be a macro, so I've made that a function. Furthermore (when (boundp 'swank::*inspector-dwim-lookup-hooks*) ..) should maybe be under #+slime-dwim-branch, but I did not change that yet.
- Willem