docs: function (actual, message) {
          YUITest.Assert._increment();
          var shouldFail = false;
          if (Array.isArray){
              shouldFail = !Array.isArray(actual);
          } else {
              shouldFail = Object.prototype.toString.call(actual) != "[object Array]";
          }
          if (shouldFail){
              throw new YUITest.UnexpectedValue(YUITest.Assert._formatMessage(message, "Value should be an array."), actual);
          }
      }