stub-example.js

import user from './user'

describe('user', () => {
  
  // before each test
  beforeEach(() => {
    // spy on the "isValid" function on the "user" object
    jest.spyOn(user, 'isValid');
  })
  
  // after each test
  afterEach(() => {
    // remove the mock from the "isValid" function
    user.isValid.mockRestore();
  })
  
  it('is validated for valid users', () => {
    user.isValid.mockReturnValue(true)
    
    // Testing someFn with user where user.isValid() returns true
    assert(validate(user))
  })
  
  it('does not validated for invalid users', () => {
    user.isValid.mockReturnValue(false)

    // Testing someFn with user where user.isValid() returns true
    assert(!validate(user))
  })
})