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; /         


        

Answer 1

You could use Object.defineProperty

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

Answer 2

OMG I've been here so many times. Finally figure out the proper solution for this. If you care about spying only. Go for @Franey 's answer. However if you actually need to stub a value for the getter this is how you can do it

class Awesomeness {
  get isAwesome() {
    return true
  }
}

describe('Awesomeness', () => {
  it('is not always awesome', () => {
    const awesomeness = new Awesomeness
    jest.spyOn(awesomeness, 'isAwesome', 'get').mockReturnValue(false)

    expect(awesomeness.isAwesome).toEqual(false)
  })
})

Answer 3

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')