Node / Express / Mocha disable middleware?

Question

I have a hello world app which looks like this:

let clientAuthMiddleware = () => (req, res, next) => {
  if (!req.client.authorized) {
    return res.status(401).send('Invalid client certificate authentication.');
  }
  return next();
};

function app() {
    const fs = require('fs');
    const https = require('https');
    const express = require('express');

    const app = express();
    app.use(clientAuthMiddleware());

    app.get('/', (req, res) => {
      console.log(req.socket.getPeerCertificate());
      return res.send('Hello world!');
    });

    https
      .createServer(
        {
          cert: fs.readFileSync('cert/localhost.crt'),
          key: fs.readFileSync('cert/localhost.key'),        
          requestCert: true,
          rejectUnauthorized: false,
          ca: fs.readFileSync('cert/ca.crt'),
        },
        app
      )
      .listen(9443);
    
    return app;
}

if (require.main === module) instance = app()
module.exports.app = app
module.exports.authMiddleware = clientAuthMiddleware

And a test which looks like:

 describe('GET /', function() {
    it('should return Hello world!', function(done) {
          chai.request(app.app()).get('/')
             .end((err, res) => {
                 if (err)done(err);
                 res.should.have.status(200);
                 expect(res.body).to.equal('Hello world!');
                 done();
              });
    });
  });

How can I replace authMiddleware in the test, preferably without using some external stubbing library? Isn't there some way I can just rearrange my code so in the test I can just do app.authMiddleware = {my own stub function}?

Edit: Also, is there a way I can just straightforwardly unit test these endpoints like app.get('/') without making a real HTTP request? I keep searching Google for unit testing Node/Express with Mocha and every resource I find seems to be functional testing making a real request....

Answer 1

You can specify in your app using environment variables, if your environment is test or production or development. write condition fro middlware something like this

 if(process.env.NODE_ENV !== 'test') { 
        app.use(clientAuthMiddleware()); 
 } 

And if you want to test your app without making HTTP request, you need to separate the business logic from request handlers.

For example if you have a route "/api/user/login", for the route you have a route hanlder something like

 app.post("/api/user/login" , async (req,res) => {
    const response = await login(req.body.email,req.body.password);
    res.status(200).json(response);
 });

 // login function is independent of express 
 // routes and can be easily tested  without api requests
 async function login(email,password) {
    //login logic
 }

In this way you can make your business logic independent of express and it can be easily tested without HTTP requests.