"use strict"; class Base { get test() { return 1; } }; class Obj extends Base { set() { return super.test = 3; } } Object.defineProperty(Obj.prototype, 'test', { value: 2, writable: true, configurable: true, }); const obj = new Obj(); expect(() => { // this requires helpers to be in file (not external), so they // are in "strict" mode code. obj.set(); }).toThrow(); expect(Base.prototype.test).toBe(1); expect(Obj.prototype.test).toBe(2); expect(obj.test).toBe(2);