anchor.diff:    } else {
       return stack.toString();
     }
  - 
  -  // Calculate the max width of first column so we can 
  +
  +  // Calculate the max width of first column so we can
     // pad to align the second columns.
     int padding = lines.fold(0, (n, line) {
       var match = _frameRegExp.firstMatch(line);
  
positive.code: 
  // Stack formatting utility. Strips extraneous content from a stack trace.
  // Stack frame lines are parsed with a regexp, which has been tested
  // in Chrome, Firefox and the VM. If a line fails to be parsed it is 
  // included in the output to be conservative.
  //
  // The output stack consists of everything after the call to TestCase._run.
  
negative.code: Configuration _config;
  
  /**
   * [Configuration] used by the unittest library. Note that if a
   * configuration has not been set, calling this getter will create
   * a default configuration.
   */
  