anchor.diff:    }
   }
   
  -class AssersionException implements Exception {
  +class AssertionException implements Exception {
     String msg;
     
  -  AssersionException.msg(this.msg) : super() ;
  +  AssertionException.msg(this.msg) : super() ;
   }
   
   typedef bool _op(StringBuffer buffer, bool result);
  
positive.code:     }
  
      if(result == false){
        throw new AssersionException.msg("expected is ${buffer.toString()}<${expect}>, but got <${actual}>.");
      }
    }
  }
  
negative.code:     start = true;
      try{
        test();
      } catch(AssertionException e) {
        errorMessage = e.msg;
        error = e;
        return;
  