anchor.diff:    (:documentation
      "Result of a failed error assertion."))
   
  -(defun error-result (test expected actual)
  +(defmethod assert-result ((type (eql :error)) test expected actual)
     "Return the result of an error assertion."
     (declare (ignore test))
     (or
  
positive.code:   (:documentation
     "Result of a failed output assertion."))
  
  (defun output-result (test expected actual)
    "Return the result of an output assertion."
    (declare (ignore test))
    (string=
     (string-trim '(#\newline #\return #\space) (car actual))
     (car expected)))
  
  (defun assert-function (type)
    "Return the function for the assertion type."
    (ecase type
      (:equal #'equal-result)
      (:error #'error-result)
      (:macro #'macro-result)
      (:result #'boolean-result)
      (:output #'output-result)))
  
  (defun assert-class (type)
    "Return the class for the assertion type."
  
negative.code:   `(lambda ()
       (list ,@(mapcan (lambda (form) (list `',form form)) extras))))
  
  (defgeneric assert-result (type test expected actual)
    (:documentation
     "Return the result of the assertion."))
  
  (defclass failure-result ()
    ((form
      :initarg :form
  