code: function(coverage){
  
          var report = {};
          for (var prop in coverage){
              if (coverage.hasOwnProperty(prop)){
                  report[prop] = coverage[prop].lines;
              }
          }
  
          return YUITest.Util.JSON.stringify(coverage);
      }
docs: Returns the coverage report in a JSON format compatible with
  Xdebug. See <a href="http://www.xdebug.com/docs/code_coverage">Xdebug Documentation</a>
  for more information. Note: function coverage is not available
  in this format.
  @param {Object} coverage The coverage report object.
  @return {String} A JSON-formatted string of coverage data.
  @method XdebugJSON
  @namespace YUITest.CoverageFormat