The Tor Browser / file revision

 // Superficial tests for iterators created by Array.prototype.iterator

 load(libdir + "iteration.js");

 var proto = Object.getPrototypeOf([][std_iterator]());

 assertEq(Object.getPrototypeOf(proto), Iterator.prototype);

 proto = Object.getPrototypeOf([].keys());

 assertEq(Object.getPrototypeOf(proto), Iterator.prototype);

 proto = Object.getPrototypeOf([].entries());

 assertEq(Object.getPrototypeOf(proto), Iterator.prototype);

 function check(it) {

     assertEq(typeof it, 'object');

     assertEq(Object.getPrototypeOf(it), proto);

     assertEq(Object.getOwnPropertyNames(it).length, 0);

     assertEq(it[std_iterator](), it);

     // for-in enumerates the iterator's properties.

     it.x = 0;

     var s = '';

     for (var p in it)

         s += p + '.';

     assertEq(s, 'x.');

 }

 check([][std_iterator]());

 check(Array.prototype[std_iterator].call({}));

 check([].keys());

 check(Array.prototype.keys.call({}));

 check([].entries());

 check(Array.prototype.entries.call({}));