testcase for Object.prototype.__proto__

ecmascript-testcases/test-bi-object-proto-__proto__.js

@@ -0,0 +1,61 @@
+/*
+ *  Object.prototype.__proto__ (ES6)
+ */
+
+/*===
+__proto__ exists in Object.prototype: true
+__proto__ property descriptor: enumerable: false configurable: true set exists: true get exists: true
+literal {}: true
+literal []: true
+before: true 123 undefined
+after: true 123 321
+TypeError
+===*/
+
+function test() {
+    var o, pd;
+    var a, b;
+
+    // __proto__ existence
+    print('__proto__ exists in Object.prototype:', '__proto__' in Object.prototype);
+
+    // Rhino and V8 print true above (Object.prototype.__proto__ exists) but
+    // the descriptor here will be undefined for some reason!
+    pd = Object.getOwnPropertyDescriptor(Object.prototype, '__proto__');
+    if (pd) {
+        print('__proto__ property descriptor:', 'enumerable:', pd.enumerable,
+              'configurable:', pd.configurable, 'set exists:', (typeof pd.set === 'function'),
+              'get exists:', (typeof pd.get === 'function'));
+    } else {
+        print('__proto__ property descriptor is undefined');
+    }
+
+    // A few read checks for built-ins
+    o = {};
+    print('literal {}:', o.__proto__ === Object.prototype);
+
+    o = [];
+    print('literal []:', o.__proto__ === Array.prototype);
+
+    // Setting a prototype
+    a = { foo: 123 };
+    b = { bar: 321 };
+    print('before:', a.__proto__ === Object.prototype, a.foo, a.bar);
+    a.__proto__ = b;
+    print('after:', a.__proto__ === b, a.foo, a.bar);
+
+    // Attempt to set a prototype loop
+    try {
+        b.__proto__ = a;
+        print('never here');
+    } catch (e) {
+        // Rhino throws InternalError, ES6 specifies TypeError
+        print(e.name);
+    }
+}
+
+try {
+    test();
+} catch (e) {
+    print(e);
+}