This is the most useful thing since macros: sb-cover.
No nonsense code coverage:
;;; The code coverage module
;;; Enable instrumentation
(declaim (optimize sb-cover:store-coverage-data))
;;; Force recompilation with instrumentation
(asdf:oos 'asdf:load-op :my-project-test :force t)
;;; Run the tests!
;;; Create the report
;;; Disable instrumentation
(declaim (optimize (sb-cover:store-coverage-data 0)))
See Code coverage tool for SBCL for some nice output as well. I had no idea the cl-ppcre tests had such good coverage. Damn.