Testing node express app with supertest on cloud9

Testing node express app with supertest on cloud9

I can't test express apps on cloud9 with supertest : even basic tests
throws ECONNREFUSED.
Steps to reproduce :
create a new nodejs workspace
npm install express supertest
create a file "fails.js" containing the following code :
// Code from supertest page
var request = require('supertest')
, express = require('express');
var app = express();
app.get('/user', function(req, res){
res.send(201, { name: 'tobi' });
});
request(app)
.get('/user')
.expect('Content-Type', /json/)
.expect('Content-Length', '20')
.expect(201)
.end(function(err, res){
if (err) throw err;
});
then launch node fails.js on terminal : Error: connect ECONNREFUSED
jmbarbier@test:~/606588 $ node fails.js
/var/lib/stickshift/522b68364382ecb9de0000ac/app-root/data/606588/fails.js:16
if (err) throw err
^
Error: connect ECONNREFUSED
at errnoException (net.js:906:11)
at Object.afterConnect [as oncomplete] (net.js:897:19)
I've no idea of what's going on...