The Tor Browser / file revision

 // Copyright 2009 the Sputnik authors.  All rights reserved.

 // This code is governed by the BSD license found in the LICENSE file.

 /**

  * If Type(Primitive(x)) is not String and Type(Primitive(y)) is not String, then operator x + y returns ToNumber(x) + ToNumber(y)

  *

  * @path ch11/11.6/11.6.1/S11.6.1_A3.1_T2.3.js

  * @description Type(Primitive(x)) is different from Type(Primitive(y)) and both types vary between Number (primitive or object) and Undefined

  */

 //CHECK#1

 if (isNaN(1 + undefined) !== true) {

   $ERROR('#1: 1 + undefined === Not-a-Number. Actual: ' + (1 + undefined));

 }

 //CHECK#2

 if (isNaN(undefined + 1) !== true) {

   $ERROR('#2: undefined + 1 === Not-a-Number. Actual: ' + (undefined + 1));

 }

 //CHECK#3

 if (isNaN(new Number(1) + undefined) !== true) {

   $ERROR('#3: new Number(1) + undefined === Not-a-Number. Actual: ' + (new Number(1) + undefined));

 }

 //CHECK#4

 if (isNaN(undefined + new Number(1)) !== true) {

   $ERROR('#4: undefined + new Number(1) === Not-a-Number. Actual: ' + (undefined + new Number(1)));

 }