如何在玩笑中模拟函数内的变量

Question

我想开玩笑地测试“canViewPage”方法。如何模拟 const userPages 这是来自 func getUserPage 的值

   canViewPage(page){
     const userPages = getUsersPages();
    if(userPages.includes(page)){
      return true;
    }
    return false;
   }


  getUsersPages(){
    // here i hardcode a list of pages, for simplicity purposes
    const pages = ['home','about','contact'];
    return pages

  }

这是我尝试过的

test('test canViewPage', () => {
    const spy = jest.spyOn(canViewPage, 'userPages');
    spy.mockReturnValue(['home','about','contact']);

    expect(canViewPage('premiumPage')).toBe(false); 

    spy.mockRestore();
  });

我也尝试过这个

test('test canViewPage', () => {
    const spy = jest.spyOn(canViewPage, 'getUsersPage');
    spy.mockReturnValue(['home','about','contact']);

    expect(canViewPage('premiumPage')).toBe(false); 

    spy.mockRestore();
  });

Answer 1

要嘲笑 的价值，userPages你必须嘲笑getUserPage。要实现这一点，取决于 和getUserPage的canViewPage定义位置和方式。我假设这两个函数是在类中定义的MyAwesomeClass

// MyAwesomeClass.js
export default class MyAwesomeClass {
  canViewPage(page) {
    const userPages = this.getUsersPages();
    if (userPages.includes(page)) {
      return true;
    }
    return false;
  }


  getUsersPages() {
    // here i hardcode a list of pages, for simplicity purposes
    const pages = ['home', 'about', 'contact'];
    return pages;
  }
}

// test.js
import MyAwesomeClass from '<path to MyAwesomeClass.js>'
test('test canViewPage', () => {
  const instance = new MyAwesomeClass()
  const spy = jest.spyOn(instance, 'getUsersPages');
  spy.mockReturnValue(['mockItem1','mockItem2','mockItem3']);

  expect(instance.canViewPage('premiumPage')).toBe(false);
  expect(instance.canViewPage('mockItem1')).toBe(true);

  spy.mockRestore();
});

如果canViewPage和getUsersPages是类中的静态方法，则以不同的方式进行模拟

test('test canViewPage', () => {
  const spy = jest.spyOn(MyAwesomeClass, 'getUsersPages');
  spy.mockReturnValue(['mockItem1','mockItem2','mockItem3']);

  expect(MyAwesomeClass.canViewPage('premiumPage')).toBe(false);
  expect(MyAwesomeClass.canViewPage('mockItem3')).toBe(true);

  spy.mockRestore();
});