How to mock the value of a property in Node/Express using Jest-CodePudding

I am new to jest. I have a function where I validate the length of a property. If the length is exceeded, then the function returns the response with the 400 status code.

Config.js

module.exports = {
    maxLength: 50
}

Controller.js

const {
    maxLength
} = require("../config")

const sendMessage = (req, res) => {
        const {
            message
        } = req.body
        if (message.length > maxLength) {
            {
                res.status(400).send()
            }
}

I want to mock the value of maxLength to 2 when I write the unit tase. So that I can check without passing too many messages.

I have tried the following.

Controller.test.js

const config = require("../config")

confif.maxLimit=jest.fn()

describe('Cntroller.sendMessage', () => {
            it("should return 400 if the message length exceed", async () => {
                config.maxLength = 2;
                req.body = {
                    message: "hello I am new message"
                }
                await sendMessage(req, res)
                expect(res.statusCode).toBe(400)
            )
)

Here I have tried to mock the value of maxLength to 2 and the message length is 23. So the response status code will be 400. But the test has failed.

Expected(400)

Recieved(200)

How to mock the value of maxLength?

Thanks in advance!

CodePudding user response：

This will mock the maxLength to different value:

jest.mock("../config", () => ({
  maxLength: 2
}))

As the maxLength is not a function I am not sure how could you change the mocked value to have different value for different test.