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

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;