text: // Copyright 2009 the Sputnik authors.  All rights reserved.
  /**
   * Operator x - y returns ToNumber(x) - ToNumber(y)
   *
   * @path ch11/11.6/11.6.2/S11.6.2_A3_T1.4.js
   * @description Type(x) and Type(y) vary between Null and Undefined
   */
  
  //CHECK#1
  if (isNaN(null - undefined) !== true) {
    $ERROR('#1: null - undefined === Not-a-Number. Actual: ' + (null - undefined));
  }
  
  //CHECK#2
  if (isNaN(undefined - null) !== true) {
    $ERROR('#2: undefined - null === Not-a-Number. Actual: ' + (undefined - null));
  }
  
  //CHECK#3
  if (isNaN(undefined - undefined) !== true) {
    $ERROR('#3: undefined - undefined === Not-a-Number. Actual: ' + (undefined - undefined));
  }
  
  //CHECK#4
  if (null - null !== 0) {
    $ERROR('#4: null - null === 0. Actual: ' + (null - null));
  }
  
  