Javascript 嘲笑mock readFile，writeFile不'；不要装我的模拟

之前的一般性问题。 当我使用jest.mock（）时，我只能模拟整个模块吗？也可以导出函数、常量。 在我的app.js中，我使用例如constfilesystem=require（'fs'）。 我正在尝试测试这个应用程序，它有一个方法，可以用fs读取文件。 我现在是否必须在测试中模拟“fs”模块，或者加载app.js，然后模拟加载fs的常量

这是我的密码：

const express = require('express')
const dataFilePath = '../shoppinglist/data.json'
const fileSystem = require('fs')
let data
module.exports = {app, listener, getNewestId, getSmsFormatedShoppingList, readUpdatedData, 
dataFilePath}

app.get(baseUrl, (req, res) => {
    let finishedState
    readUpdatedData()
    if(isDataEmpty()){
      return res.status(200).send([])
    }
   if(req.query.isFinished){
        finishedState = req.query.isFinished === 'true'
    }
    const listsWithoutItems = data.data.map(({ items, ...rest }) => rest)

    const filteredList = (finishedState === true || finishedState === false)  ? sortShoppingListByFinished(listsWithoutItems, finishedState) : listsWithoutItems

    if(filteredList.length === 0){
        res.statusCode = 204
        res.send()
    }

    // adjust later, this is just used for tests
    res.setHeader('Content-Type', 'application/json')
    data.data = filteredList
    res.json(data)
    res.status(200).send()
})


function readUpdatedData(){
        let rawData = fileSystem.readFileSync(dataFilePath)
        data = JSON.parse(rawData)
        console.log(data)
        console.log('-------------------------')
}

现在我想测试api调用是否成功，读取的数据是否正确。 为此，我尝试模拟data.json，但当测试运行时，fileSystem.readFileSync（“../shoppinglist/data.json”）总是未定义。因此，我猜当它加载应用程序时，它会忽略../shoppinglist/data.json的模拟数据

describe('Get for all Lists with entries', () => {
    it('should return a list with 2 entries without items', async () => {
       jest.mock('../shoppinglist/data.json', () => ({
                    "data" : [
                        {
                            "id": 0,
                            "name": "filled shopping list",
                            "location": "lidl",
                            "targetDate": "22.03.1986",
                            "priority": 1,
                            "isFinished": false,
                            "items": [{"count":1, "name": "vodka" }, {"count":1, "name": "vodka" }
                            ]
                        }, {
                            "id": 1,
                            "name": "filled shopping list2",
                            "location": "lidl2",
                            "targetDate": "22.03.1986",
                            "priority": 1,
                            "isFinished": false,
                            "items": [{"count":1, "name": "vodka" }, {"count":1, "name": "vodka" }
                            ]
                        }
                    ]}))
        const {app} = require(appPath)
        let res
        res = await request(app)
            .get(baseUrl)
        expect(res.statusCode).toEqual(200)
        expect(res.body.data).toHaveLength(2)
        expect(res.body[0]).toEqual(expect.not.objectContaining({"items": ["vodka"]}))
        
    })
})

我也试着在测试中模拟fs，但我猜它不是这样工作的

试用后重新编辑

我已经在测试中尝试过这个：

const fs = require( 'fs')
jest.mock('fs')

describe('Get for all Lists with entries', () => {
it('should return a list with 2 entries without items', async () => {
    fs.writeFileSync.mockClear();
    fs.readFileSync.mockReturnValue('X')

  
    const {app} = require(appPath)
    let res
    res = await request(app)
        .get(baseUrl)
    expect(res.statusCode).toEqual(200)
    expect(res.body.data).toHaveLength(2)
    expect(res.body[0]).toEqual(expect.not.objectContaining({"items": 
    ["vodka"]}))
        
       })
    })

但是，当使用调用app.js时

const {app} = require(appPath)
    let res
    res = await request(app)
        .get(baseUrl)

readUpdateData方法始终在rawData处未定义，就像mock永远不会被重试一样

function readUpdatedData(){
    let rawData = fileSystem.readFileSync(dataFilePath)
    data = JSON.parse(rawData)
    module.exports = data
    console.log(data)
    console.log('-------------------------')
 }

---

我现在找到了解决办法

const mockReadFile = jest.spyOn(fs, 'readFileSync')
mockReadFile.mockImplementation(() =>  JSON.stringify({
        "data" : [
            {
                "id": 0,
                "name": "filled shopping list",
                "location": "lidl",
                "targetDate": "22.03.1986",
                "priority": 1,
                "isFinished": false,
                "items": [{"count":1, "name": "vodka" }, {"count":1, "name": "vodka" }
                ]
            }, {
                "id": 1,
                "name": "filled shopping list2",
                "location": "lidl2",
                "targetDate": "22.03.1986",
                "priority": 1,
                "isFinished": false,
                "items": [{"count":1, "name": "vodka" }, {"count":1, "name": 
                "vodka" }
                ]
                }
                ]}))

这样，就可以正确地从模拟中读取数据