JSTests/test262/test/language/expressions/delete/11.4.1-4.a-3.js

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

/*---
info: |
    This test is actually testing the [[Delete]] internal method (8.12.8). Since the
    language provides no way to directly exercise [[Delete]], the tests are placed here.
es5id: 11.4.1-4.a-3
description: >
    delete operator returns false when deleting a non-configurable
    data property
flags: [noStrict]
---*/

  var o = {};
  var desc = { value : 1, configurable: false }; // all other attributes default to false
  Object.defineProperty(o, "foo", desc);
  
  // Now, deleting o.foo should fail because [[Configurable]] on foo is false.
  var d = delete o.foo;

assert.sameValue(d, false, 'd');
assert.sameValue(o.hasOwnProperty("foo"), true, 'o.hasOwnProperty("foo")');