Question

我想开玩笑地测试'canViewPage方法。如何模拟const userPages，这是func getUserPage中的值

   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

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

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

    spy.mockRestore();
  });

Answer 1

要模拟userPages的值，您必须模拟getUserPage。为此，取决于getUserPage和canViewPage的定义位置和定义方式。我假设这两个函数在类MyAwesomeClass

中定义

// 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，则模拟方式会不同

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();
});

Answer 2

建议使用间谍和存根，但是如果您要访问外部作用域对象，可以修改窗口变量并为其分配所需的值

例如：

var a = 10;
const myfun = () => {
 return a + 20;
}

test('myfun', () => {
  window.a = 20
  expect(myfun).toBe(40)
 }

如何在玩笑的函数内部模拟变量

2 个答案: