(unwind-protect
     (progn
       (defclass (foo bar) () ())
       (defclass baz () ())
       (defgeneric frob (x y))
       (defmethod frob ((x (foo bar)) (y baz))
         (declare (ignore x)) 42)
       (is (= (eval '(frob (make-instance '(foo bar))
                      (make-instance 'baz)))
              42)))
  (setf (find-class '(foo bar)) nil)
  (setf (find-class 'baz) nil)
  (fmakunbound 'frob))