anchor.diff:  (register-m1-m2-pair 'test1-mixin 'meta1)
   (register-m1-m2-pair 'test2-mixin 'meta2)
   
  -(with-metap-ensured
  -  (defclass test1 (test1-mixin) ())
  -  (defclass test2 (test2-mixin) ()))
  +(defclass test1 (test1-mixin) ())
  +(defclass test2 (test2-mixin) ())
   
   (test meta-propagation-test
     (is (eq (class-of (find-class 'test2)) (find-class 'meta2)))
  
positive.code: 
  (test illegale-specifing-case-test
    (signals simple-error
      (with-metap-ensured (defclass test2-2 (test2-mixin) () (:metaclass meta1))))
    (signals simple-error
      (with-metap-ensured (defclass test2-3 (test2-mixin) () (:metaclass meta2)))))
  
negative.code: (in-package :metap-test)
  
  (in-suite* all)
  
  (metap:enable-metap)
  
  (defclass a () ())
  (defclass b (a) ())
  