Mocking up static methods in jest

Question

I am having trouble mocking up a static method in jest. Immagine you have a class A with a static method:

export default class A {   f() {     return 'a.f()'   }    static staticF () {     return 'A.staticF()'   } } 

And a class B that imports A

import A from './a'  export default class B {   g() {     const a = new A()     return a.f()     }    gCallsStaticF() {     return A.staticF()   } } 

Now you want to mock up A. It is easy to mock up f():

import A from '../src/a' import B from '../src/b'  jest.mock('../src/a', () => {   return jest.fn().mockImplementation(() => {     return { f: () => { return 'mockedA.f()'} }   }) })  describe('Wallet', () => {   it('should work', () => {     const b = new B()     const result = b.g()     console.log(result) // prints 'mockedA.f()'   }) }) 

However, I could not find any documentation on how to mock up A.staticF. Is this possible?

Answer 1

You can just assign the mock to the static method

import A from '../src/a' import B from '../src/b'  jest.mock('../src/a')  describe('Wallet', () => {     it('should work', () => {         const mockStaticF = jest.fn().mockReturnValue('worked')          A.staticF = mockStaticF          const b = new B()          const result = b.gCallsStaticF()         expect(result).toEqual('worked')     }) })