1.3.1 • Public • Published

Quick and dirty Express Router mock

With version 1.0, this now supports Express 4.0 routes.

This provides a mock express object that you can attach routes to.

The motivation was this is to have a mechanic for pure Unit Testing of routes which doesn't rely on creating an instance of Express. Additionally, I wanted to pass in mock request and response objects that I could later inspect for changes made by the controller.

Quick start

Create a mock express application:

var MockExpress = require('mock-express'),
	assert = require('assert');

var app = MockExpress(); // notice there's no "new"

Append a get route to your app

app.get('/test', function(req, res, next) {
	var model = { name: 'world'};

	if (req.query.start === 'true') {
		res.render('index', model);
	} else {

Create and supply your own mock req and res objects:

var req = app.makeRequest({ 'host': '' });
var res = app.makeResponse(function(err, sideEffects) {
	assertEqual(, 'world');
	done(); // this is the callback used by mocha to indicate test completion

Call the route

app.invoke('get', '/test?start=true', req, res);

Note that your assertions should be in the callback passed to the makeResponse object, since most routes terminate with some kind of call to the response object.

With the transition to Express 4.x, this module now supports the use of router.use() syntax, which allows you to test error-handling middleware.

You do not need to pass in the req and res objects when calling invoke() if you use makeRequest and makeResponse. invoke() will automatically default to the last request and response mock objects made using those utility functions. Thus you could write app.invoke('get', '/test?start=true') above instead.

Timeouts due to assertion errors in callbacks

If your assertions in the callbacks throw an error, then the test will timeout because the error is thrown in a callback.

To avoid this, create your callback as follows:

var assertionCallback = app.makeAssertionCallback(done, function(err, sideEffects) {
	<your assertions>
var res = app.makeResponse();

Note that you should not call done() (or it's non-Mocha equivalent) directly if you create your callback in this manner.

Available side effects

Currently you have the following available to check

  • sideEffects.redirect - this string represents the name of any redirect
  • sideEffects.viewName - the view name passed as the first argument to res.render.
  • sideEffects.model - the model object passed as the second argument to res.render
  • sideEffects.session - anything that is set into the session object.
  • sideEffects.json - the variable passed as the first argument to res.json
  • sideEffects.send - the variable passed as the first argument to res.send




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