How to mock/replace getter function of object with Jest?

Question

In Sinon I can do the following:

var myObj = {     prop: 'foo' };  sinon.stub(myObj, 'prop').get(function getterFn() {     return 'bar'; });  myObj.prop; // 'bar' 

But how can I do the same with Jest? I can't just overwrite the function with something like jest.fn(), because it won't replace the getter

"can't set the value of get"

Answer 1

For anyone else stumbling across this answer, Jest 22.1.0 introduced the ability to spy on getter and setter methods.

Edit: like in scieslak's answer below, because you can spy on getter and setter methods, you can use Jest mocks with them, just like with any other function:

class MyClass {   get something() {     return 'foo'   } }  jest.spyOn(MyClass, 'something', 'get').mockReturnValue('bar') const something = new MyClass().something  expect(something).toEqual('bar') 

Answer 2

You could use Object.defineProperty

Object.defineProperty(myObj, 'prop', {   get: jest.fn(() => 'bar'),   set: jest.fn() });