Test for function.prototype's property descriptor. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS descriptor['writable'] is true PASS descriptor['enumerable'] is false PASS descriptor['configurable'] is false PASS descriptor['writable'] is true PASS descriptor['enumerable'] is false PASS descriptor['configurable'] is false PASS Object.defineProperty(c, 'prototype', { get: function(){} }) threw exception TypeError: Attempting to change access mechanism for an unconfigurable property.. PASS descriptor['writable'] is true PASS descriptor['enumerable'] is false PASS descriptor['configurable'] is false PASS successfullyParsed is true TEST COMPLETE