javascript-使用jest测试另一个函数内的函数

我如何使用玩笑测试以下代码段.我正在尝试测试Winston自定义格式printf

// sample.js

import {aa:{b}} = require("thirparty-package")

const a = () => {
   return b((log) => {
     return `log message will be ${log.message}`
   })
}

module.exports = {
  a
}


// sample.test.js
const customFunctions = require('./sample')

test('should check b function is called and returns a string', () => {
   expect(customFunctions.a).toHaveBeenCalled() // throwing error 
    //jest.fn() value must be a mock function or spy.
})

解决方法:

如果需要测试的是b,则应该是间谍,而不是a.

应该模拟第三方模块(一个demo)：

const bMock = jest.fn();
jest.mock('thirparty-package', () => ({ aa: { b: bMock } }));
const { a } = require('./sample');
a();
const callback = bMock.mock.calls[0][0]; 
expect(callback).toEqual(expect.any(Function));
expect(callback({ message: 'foo' })).toBe('log message will be foo');

标签：javascript,node-js,jestjs
来源： https://codeday.me/bug/20191013/1909402.html