How does one unit test routes with Express?


I'm in the process of learning Node.js and have been playing around with Express. Really like the framework;however, I'm having trouble figuring out how to write a unit/integration test for a route.

Being able to unit test simple modules is easy and have been doing it with Mocha; however, my unit tests with Express fail since the response object I'm passing in doesn't retain the values.

Route-Function Under Test (routes/index.js):

exports.index = function(req, res){
  res.render('index', { title: 'Express' })

Unit Test Module:

var should = require("should")
    , routes = require("../routes");

var request = {};
var response = {
    viewName: ""
    , data : {}
    , render: function(view, viewData) {
        viewName = view;
        data = viewData;

describe("Routing", function(){
    describe("Default Route", function(){
        it("should provide the a title and the index view name", function(){
        routes.index(request, response);


When I run this, it fails for "Error: global leaks detected: viewName, data".

  1. Where am I going wrong so that I can get this working?

  2. Is there a better way for me to unit test my code at this level?

Update 1. Corrected code snippet since I initially forgot "it()".

3/1/2012 2:38:15 PM

Accepted Answer

Change your response object:

var response = {
    viewName: ""
    , data : {}
    , render: function(view, viewData) {
        this.viewName = view; = viewData;

And it will work.

3/1/2012 2:39:53 PM

As others have recommended in comments, it looks like the canonical way to test Express controllers is through supertest.

An example test might look like this:

describe('GET /users', function(){
  it('respond with json', function(done){
      .set('Accept', 'application/json')
      .end(function(err, res){
        if (err) return done(err);

Upside: you can test your entire stack in one go.

Downside: it feels and acts a bit like integration testing.

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