code: function (expectedType, actualValue, message){
          YUITest.Assert._increment();
          if (typeof actualValue != expectedType){
              throw new YUITest.ComparisonFailure(YUITest.Assert._formatMessage(message, "Value should be of type " + expectedType + "."), expectedType, typeof actualValue);
          }
      }
docs: Asserts that a value is of a particular type.
  @param {String} expectedType The expected type of the variable.
  @param {Object} actualValue The actual value to test.
  @param {String} message (Optional) The message to display if the assertion fails.
  @method isTypeOf
  @static