The Tor Browser / file revision

 // Set surfaces

 load(libdir + "iteration.js");

 var desc = Object.getOwnPropertyDescriptor(this, "Set");

 assertEq(desc.enumerable, false);

 assertEq(desc.configurable, true);

 assertEq(desc.writable, true);

 assertEq(typeof Set, 'function');

 assertEq(Object.keys(Set).length, 0);

 assertEq(Set.length, 0);

 assertEq(Set.name, "Set");

 assertEq(Object.getPrototypeOf(Set.prototype), Object.prototype);

 assertEq(Object.prototype.toString.call(Set.prototype), "[object Set]");

 assertEq(Object.prototype.toString.call(new Set), "[object Set]");

 assertEq(Object.prototype.toString.call(Set()), "[object Set]");

 assertEq(Object.keys(Set.prototype).join(), "");

 assertEq(Set.prototype.constructor, Set);

 function checkMethod(name, arity) { 

     var desc = Object.getOwnPropertyDescriptor(Set.prototype, name);

     assertEq(desc.enumerable, false);

     assertEq(desc.configurable, true);

     assertEq(desc.writable, true);

     assertEq(typeof desc.value, 'function');

     assertEq(desc.value.name, name);

     assertEq(desc.value.length, arity);

 }

 checkMethod("has", 1);

 checkMethod("add", 1);

 checkMethod("delete", 1);

 checkMethod("values", 0);

 checkMethod("entries", 0);

 var desc = Object.getOwnPropertyDescriptor(Set.prototype, "size");

 assertEq(desc.enumerable, false);

 assertEq(desc.configurable, true);

 assertEq(typeof desc.get, 'function');

 assertEq(desc.get.length, 0);

 assertEq(desc.set, undefined);

 checkMethod("clear", 0);

 // Set.prototype.keys, .values, and .iterator are the same function object

 assertEq(Set.prototype.keys, Set.prototype.values);

 assertEq(Set.prototype[std_iterator], Set.prototype.values);