Unit testing expressjs application

Question

I have the following module that I'm working on adding unit tests for. Basically I want to ensure that app.use is called with / and the appropriate handler this.express.static('www/html') , I also want to ensure that app.listen is called with the correct port.

function WebService(express, logger) {
    this.express = express;
    this.log = logger;
    this.port = 3000;
}

// init routes and start the server
WebService.prototype.start = function start() {    
    var app = this.express();

    // Setup routes
    app.use('/', this.express.static('www/html'));

    // Startup the server
    app.listen(this.port);

    this.log.info('Starting webserver on port %s', this.port);

};

module.exports = WebService;

If I remove the app.use (replace with a simple app.get) I can get the listen tested by passing this into the constructor in the unit test

var express_stub = function() {
                var tmpObj = {
                    get: function() {},
                    listen: listen_stub // sinonjs stub
                };
                return tmpObj;
            };

When I switch over to using this.express.static in the route, this falls over (expectedly because this.express doesn't define static) I can't quite get my head wrapped around the correct way to deal with this. The this.express() as the constructor is really throwing me. I can't figure out the correct way to mock the calls I want to validate in express.

Answer 1

You can use Supertest

var request = require('supertest')
  , express = require('express');

var app = express();

app.get('/user', function(req, res){
  res.send(200, { name: 'tobi' });
});

request(app)
  .get('/user')
  .expect('Content-Type', /json/)
  .expect('Content-Length', '20')
  .expect(200)
  .end(function(err, res){
if (err) throw err;
  });

Using Mocha:

describe('GET /users', function(){
  it('respond with json', function(done){
    request(app)
      .get('/user')
      .set('Accept', 'application/json')
      .expect('Content-Type', /json/)
      .expect(200, done);
  })
})

I suggest you to divide into two file your app: the app.js that contains all your app code and return it with module.exports, and the server.js file that requires app.js and pass it to a new http server listen method. This way you can write tests doing require of app.js.

This is how the default app created with express generator work.