anchor.diff:                             (drawing-test-name test))))))))
   
   (defun drawing-test-raster-image (test format &optional filename)
  -  (let* ((test (if (stringp test) (gethash test *drawing-tests*) test))
  +  (let* ((test (if (symbolp test) (gethash test *drawing-tests*) test))
            (filename (or filename (format nil "/tmp/~a-~a.~(~a~)"
                                           (drawing-test-category test)
                                           (drawing-test-name test) format)))
  
positive.code: (defstruct drawing-test category name description display-function)
  
  (defun drawing-test-keyname (category name)
    (concatenate 'string category "-" name))
  
  (defmacro define-drawing-test (category name (frame stream &rest arglist) description &body body)
    (check-type category string)
  
negative.code: ;;; Clipping
  ;;;
  
  (define-drawing-test "Clipping Region" "ellipse" (frame stream)
      "Non-rectangular clipping region. We should see grey rotated ellipse with
  limited angle drawn inside green border. This ellipse is a clipping region. Then
  we randomly drawn points on the screen which should be clipped to the grey area."
  