JSTests/test262/test/built-ins/Object/defineProperty/15.2.3.6-4-5.js

// Copyright (c) 2012 Ecma International.  All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.

/*---
info: >
    Step 4 of defineProperty calls the [[DefineOwnProperty]] internal method
    of O to define the property. Step 6 of [[DefineOwnProperty]] returns if
    every field of desc also occurs in current and every field in desc has
    the same value as current.
es5id: 15.2.3.6-4-5
description: >
    Object.defineProperty is no-op if current and desc are the same
    data desc
---*/

  function sameDataDescriptorValues(d1, d2) {
    return (d1.value === d2.value &&
            d1.enumerable === d2.enumerable &&
            d1.writable === d2.writable &&
            d1.configurable === d2.configurable);
  }

  var o = {};

  // create a data valued property with the following attributes:
  // value: 101, enumerable: true, writable: true, configurable: true
  o["foo"] = 101;

  // query for, and save, the desc. A subsequent call to defineProperty
  // with the same desc should not disturb the property definition.
  var d1 = Object.getOwnPropertyDescriptor(o, "foo");  

  // now, redefine the property with the same descriptor
  // the property defintion should not get disturbed.
  var desc = { value: 101, enumerable: true, writable: true, configurable: true };
  Object.defineProperty(o, "foo", desc);

  var d2 = Object.getOwnPropertyDescriptor(o, "foo"); 

assert.sameValue(sameDataDescriptorValues(d1, d2), true, 'sameDataDescriptorValues(d1, d2)');