Test RegExp#toString On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS Object.getOwnPropertyDescriptor(RegExp.prototype, 'toString').configurable is true PASS Object.getOwnPropertyDescriptor(RegExp.prototype, 'toString').enumerable is false PASS Object.getOwnPropertyDescriptor(RegExp.prototype, 'toString').get is undefined PASS Object.getOwnPropertyDescriptor(RegExp.prototype, 'toString').set is undefined PASS typeof Object.getOwnPropertyDescriptor(RegExp.prototype, 'toString').value is 'function' PASS RegExp.prototype.toString.call(new RegExp) is '/(?:)/' PASS RegExp.prototype.toString.call(new RegExp('a')) is '/a/' PASS RegExp.prototype.toString.call(new RegExp('\\\\')) is '/\\\\/' PASS RegExp.prototype.toString.call({}) is '/undefined/undefined' PASS RegExp.prototype.toString.call({source: 'hi'}) is '/hi/undefined' PASS RegExp.prototype.toString.call({ __proto__: { source: 'yo' } }) is '/yo/undefined' PASS RegExp.prototype.toString.call({source: ''}) is '//undefined' PASS RegExp.prototype.toString.call({source: '/'}) is '///undefined' PASS RegExp.prototype.toString.call(undefined) threw exception TypeError: Type error. PASS RegExp.prototype.toString.call(null) threw exception TypeError: Type error. PASS RegExp.prototype.toString.call(false) threw exception TypeError: Type error. PASS RegExp.prototype.toString.call(true) threw exception TypeError: Type error. PASS RegExp.prototype.toString.call(0) threw exception TypeError: Type error. PASS RegExp.prototype.toString.call(0.5) threw exception TypeError: Type error. PASS RegExp.prototype.toString.call('x') threw exception TypeError: Type error. PASS successfullyParsed is true TEST COMPLETE