Jest 模拟子模块功能

Question

我有一个名为client 的节点模块。它的结构如下：

//index.js
import users from "./users"

export default { users }

还有：

//users.js
export default { getUser }
function getUser(username) {
    ...
    return {role: userRole}  
}

我想在我的测试中模拟这个 getUser(username) 函数。 所以我可以这样称呼：

client.users.getUser.mockResolvedValueOnce({role: "manager"}) 

我的测试头是这样的：

let client = jest.genMockFromModule('client').default;
client.users.getUser = jest.fn();

但是，在运行我的测试时，当我的原始代码调用 client.users.getUser 时出现以下错误。

TypeError: Cannot read property 'users' of undefined

  58 | 
  59 |     // Retrieve user and then return its projects
> 60 |     client.users.getUser(username)
     |                  ^
  61 |         .then(user => {
  62 |             if (!user) {
  63 |                 throw new Error(`User ${username} not found`)

  at Object.getUser (node_modules/client/build/users.js:26:45)
  at Object.getUser [as insert] (src/web/controller/projects.js:60:18)
  at Object.insert (src/web/controller/projects.test.js:80:18)

Answer 1

你可以像这样模拟//users.js 模块：

jest.mock('./users.js', () => ({getUser: () => ({role: "manager"})})) //note that the path is relative to the test

如果您在测试期间需要不同的返回值，您可以模拟它以返回一个间谍并在测试中设置模拟返回值：

import {getUsers} from './users'
jest.mock('./users.js', () => ({getUser: jest.fn()})) 

it('does something', () => {
 getUser.mockImplementation(() => ({role: "manager"}))
})
it('does something else', () => {
 getUser.mockImplementation(() => ({role: "user"}))
})