text: // Copyright 2009 the Sputnik authors.  All rights reserved.
  // This code is governed by the BSD license found in the LICENSE file.
  
  /*---
  info: The production x += y is the same as x = x + y
  es5id: 11.13.2_A4.4_T2.4
  description: >
      Type(x) is different from Type(y) and both types vary between
      Boolean (primitive or object) and Undefined
  ---*/
  
  var x;
  
  //CHECK#1
  x = true;
  x += undefined;
  if (isNaN(x) !== true) {
    $ERROR('#1: x = true; x += undefined; x === Not-a-Number. Actual: ' + (x));
  }
  
  //CHECK#2
  x = undefined;
  x += true;
  if (isNaN(x) !== true) {
    $ERROR('#2: x = undefined; x += true; x === Not-a-Number. Actual: ' + (x));
  }
  
  //CHECK#3
  x = new Boolean(true);
  x += undefined;
  if (isNaN(x) !== true) {
    $ERROR('#3: x = new Boolean(true); x += undefined; x === Not-a-Number. Actual: ' + (x));
  }
  
  //CHECK#4
  x = undefined;
  x += new Boolean(true);
  if (isNaN(x) !== true) {
    $ERROR('#4: x = undefined; x += new Boolean(true); x === Not-a-Number. Actual: ' + (x));
  }
  