How to mock an Express/Node.js middleware on a post route? - node.js

Question

I´m writing some tests with chai and mocha and i am having some troubles.
For example, in the route that i paste down here, the LOGOUT calls the isLoggedIn middleware that checks if a user exists in the session.
For example, if a do this:
it('Logout', function(done) {
chai.request(baseURL)
.post('/logout')
.end(function(err, res) {
expect(err).to.be.null;
expect(res).to.have.status(204);
done();
});
});
the test faills cause i get a 401 status code. I am new on this test stuffs. I understand that i have to use sinon to get mi test pass, but i can´t get the solution.
This is my route:
'use strict';
const express = require('express');
const createError = require('http-errors');
const router = express.Router();
const bcrypt = require('bcrypt');
const User = require('../models/User');
const {isLoggedIn} = require('../helpers/middlewares');
router.post('/logout', isLoggedIn(), (req, res, next) => {
req.session.destroy();
return res.status(204).send();
});
This is the Middleware:
'use strict';
const createError = require('http-errors');
exports.isLoggedIn = () => (req, res, next) => {
if (req.session.user) {
next();
} else {
next(createError(401));
};
};
Thank you very much!!!

Answer 1

In your flow problem in that express middleware initialized during run express application and after becomes unavailable for stubbing. My solution is that would init stub before run express application.
test.spec.js:
const chai = require("chai"),
sinon = require("sinon"),
chaiHttp = require("chai-http"),
initServer = require("./initTestServer"),
isLoggedInMiddleware = require("./middleware");
chai.use(chaiHttp);
const { expect } = chai;
describe("Resource: /", function() {
before(function() {
sinon.stub(isLoggedInMiddleware, "isLoggedIn").callsFake(function() {
return (req, res, next) => {
next();
};
});
this.httpServer = initServer();
});
after(function() {
this.httpServer.close();
});
describe("#POST /login", function() {
beforeEach(function() {
this.sandbox = sinon.createSandbox();
});
afterEach(function() {
this.sandbox.restore();
});
it("- should login in system and return data", async function() {
return chai
.request(this.httpServer.server)
.post("/logout")
.end((err, res) => {
expect(err).to.be.null;
expect(res).to.have.status(204);
});
});
});
});
initTestServer.js:
const isLoggedInMiddleware = require("./middleware");
const initServer = () => {
const express = require("express");
const app = express();
app.post("/logout", isLoggedInMiddleware.isLoggedIn(), (req, res, next) => {
return res.status(204).send();
});
const server = require("http").createServer(app);
server.listen(3004);
const close = () => {
server.close();
global.console.log(`Close test server connection on ${process.env.PORT}`);
};
return { server, close };
};
module.exports = initServer;

Answer 2

Thank you #EduardS for then answer!!
I solved it in a similar way:
it('Logout', async function(done) {
sinon.stub(helpers, 'isLoggedIn')
helpers.isLoggedIn.callsFake((req, res, next) => {
return (req, res, next) => {
next();
};
})
app = require('../index')
chai.request(app)
.post('/api/auth/logout')
.end(function(err, res2) {
expect(res2).to.have.status(204);
helpers.isLoggedIn.restore()
})
done();
});