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easejs/test/Util/GetPropertyDescriptorTest.js

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/**
* Tests util.getPropertyDescriptor
*
* Copyright (C) 2014 Free Software Foundation, Inc.
*
* This file is part of GNU ease.js.
*
* ease.js is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
require( 'common' ).testCase(
{
caseSetUp: function()
{
this.Sut = this.require( 'util' );
this.hasGetSet = !( this.Sut.definePropertyFallback() );
},
/**
* If Object.getOwnPropertyDescriptor is provided by our environment, it
* should be used by util; anything else we do is a workaround in the
* event that this is missing.
*/
'Should use Object.getOwnPropertyDescriptor if available': function()
{
if ( !( this.hasGetSet && Object.getOwnPropertyDescriptor ) )
{
this.skip();
}
this.assertStrictEqual(
this.Sut.getOwnPropertyDescriptor,
Object.getOwnPropertyDescriptor
);
},
/**
* This function should provide a boolean value indicating whether it
* can traverse the prototype chain
*/
'Indicates whether property chain traversal is possible': function()
{
var traversable = ( typeof Object.getPrototypeOf === 'function' );
this.assertEqual(
this.Sut.getPropertyDescriptor.canTraverse,
traversable
);
},
/**
* We don't want tricksters to get funky with our system
*/
'Traversable property is non-writable': function()
{
if ( !( this.hasGetSet && Object.getOwnPropertyDescriptor ) )
{
this.skip();
}
this.assertEqual(
Object.getOwnPropertyDescriptor(
this.Sut.getPropertyDescriptor, 'canTraverse'
).writable,
false
);
},
/**
* The return value should mimic Object.getOwnPropertyDescriptor if
* we're not having to traverse the prototype chain
*/
'Acts as ES5 getOwnPropertyDescriptor when one level deep': function()
{
var obj = { foo: 'bar' },
desc1 = this.Sut.getOwnPropertyDescriptor( obj, 'foo' ),
desc2 = this.Sut.getPropertyDescriptor( obj, 'foo' )
;
this.assertDeepEqual( desc1, desc2 );
},
/**
* If we *do* have to start traversing the prototype chain (which
* Object.getOwnPropertyDescriptor() cannot do), then it should be as if
* we called Object.getOwnPropertyDescriptor() on the object in the
* prototype chain containing the requested property.
*/
'Traverses the prototype chain when necessary': function()
{
if ( !( this.Sut.getPropertyDescriptor.canTraverse ) )
{
this.skip();
}
var proto = { foo: 'bar' },
obj = function() {}
;
obj.prototype = proto;
// to give ourselves the prototype chain (we don't want to set __proto__
// because this test will also be run on pre-ES5 engines)
var inst = new obj(),
// get the actual descriptor
expected = this.Sut.getOwnPropertyDescriptor( proto, 'foo' ),
// attempt to gather the descriptor from the prototype chain
given = this.Sut.getPropertyDescriptor( inst, 'foo' )
;
this.assertDeepEqual( given, expected );
},
} );