Hi,
So, there are standard tests now for ES6!
http://samples.msdn.microsoft.com/ietestcenter/#javascript
I'd like to discuss some of the __proto__ tests at
http://samples.msdn.microsoft.com/ietestcenter/Javascript/testcases__proto_.html
# 3.1.1-10 Object.freeze(Object.prototype) disables __proto__
function testcase() {
Object.freeze(Object.prototype);
var a = new Object();
a.__proto__ = { y: 2 };
return a.y === undefined;
}
I'm not sure I see why this test should succeed. Freezing "a" should
prevent its [[Prototype]] from being changed, but I don't see why it
would be the case for Object.prototype.
(same for 3.1.1-9 for Object.seal)
# 3.1.1-11 [[DefineOwnProperty]] UnderScoreProtoEnabled is set to
true when Object.prototype is set with default values
function testcase() {
Object.defineProperty(Object.prototype, "__proto__", { writable:
true, enumerable: false, configurable: true });
var obj = {};
obj.__proto__ = { x: 10 };
return obj.x === 10;
}
I don't fully understand this test case. I think that overriding
Object.prototype.__proto__ with a data attribute should remove its magic.
(same for 3.1.1-7, 3.1.2-4-1+bcd )
# 3.1.1-4 Object.prototype.__proto__ is data property with
{writable:true, enumerable:false, configurable:true, value:null} attributes
function testcase() {
var desc = Object.getOwnPropertyDescriptor(Object.prototype,
"__proto__");
return desc.writable === true &&
desc.enumerable === false &&
desc.configurable === true &&
desc.value === null;
}
... hmm... I admire the sense of humor of whoever wrote that test.
TC39 Meeting notes from May 2013:
https://github.com/rwldrn/tc39-notes/blob/master/es6/2013-05/may-21.md#consensusresolution-5
:
__proto__ is an accessor on Object.prototype.
# 3.1.1-6 Modification of Object.prototype.__proto__ causes
UnderScoreEnabled to be set to false. Setting it to {}
function testcase() {
Object.defineProperty(Object.prototype, "__proto__", {});
var obj = new Object();
obj.__proto__ = { y: 2 };
return obj.y === undefined;
}
I believe the Object.defineProperty line is a no-op, so the test should
fail.
# 3.1.2-2-14b [[Put]] __proto__ with value {y:2} on window object
function testcase() {
window.__proto__ = { y: 2 };
return window.y === undefined;
}
window is not part of ECMAScript. This test might as well throw a
ReferenceError.
As far as the global object, I don't think it's status on [[Prototype]]
is very clear from a standard standpoint, so I would recommend not
having tests for that.
I only looked at the tests failing in Firefox, there are probably other
errors.
It would be good if the tests were reviewed carefully *before* becoming
part of any sort of "conformance" test suite.
David
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