load("test-common.js"); try { function Foo() { this.x = 123; } var foo = new Foo(); assert(foo instanceof Foo); function Base() { this.is_base = true; } function Derived() { this.is_derived = true; } Object.setPrototypeOf(Derived.prototype, Base.prototype); var d = new Derived(); assert(d instanceof Derived); assert(d instanceof Base); console.log("PASS"); } catch(e) { console.log("FAIL: " + e); }