Testing Express and Mongoose with Mocha - node.js

Question

I'm trying to test my REST API endpoint handlers using Mocha and Chai, the application was built using Express and Mongoose. My handlers are mostly of the form:
var handler = function (req, res, next) {
// Process the request, prepare the variables
// Call a Mongoose function
Model.operation({'search': 'items'}, function(err, results) {
// Process the results, send call next(err) if necessary
// Return the object or objects
return res.send(results)
}
}
For example:
auth.getUser = function (req, res, next) {
// Find the requested user
User.findById(req.params.id, function (err, user) {
// If there is an error, cascade down
if (err) {
return next(err);
}
// If the user was not found, return 404
else if (!user) {
return res.status(404).send('The user could not be found');
}
// If the user was found
else {
// Remove the password
user = user.toObject();
delete user.password;
// If the user is not the authenticated user, remove the email
if (!(req.isAuthenticated() && (req.user.username === user.username))) {
delete user.email;
}
// Return the user
return res.send(user);
}
});
};
The problem with this is that the function returns as it calls the Mongoose method and test cases like this:
it('Should create a user', function () {
auth.createUser(request, response);
var data = JSON.parse(response._getData());
data.username.should.equal('some_user');
});
never pass as the function is returning before doing anything. Mongoose is mocked using Mockgoose and the request and response objects are mocked with Express-Mocks-HTTP.
While using superagent and other request libraries is fairly common, I would prefer to test the functions in isolation, instead of testing the whole framework.
Is there a way to make the test wait before evaluating the should statements without changing the code I'm testing to return promises?

Answer 1

You should use an asynchronous version of the test, by providing a function with a done argument to it.
For more details refer to http://mochajs.org/#asynchronous-code.
Since you don't want to modify your code, one way to do that could be by using setTimeout in the test to wait before to call done.
I would try something like this:
it('Should create a user', function (done) {
auth.createUser(request, response);
setTimeout(function(){
var data = JSON.parse(response._getData());
data.username.should.equal('some_user');
done();
}, 1000); // waiting one second to perform the test
});
(There might be better way)

Answer 2

Apparently, express-mocks-http was abandoned a while ago and the new code is under node-mocks-http. Using this new library it is possible to do what I was asking for using events. It's not documented but looking at the code you can figure it out.
When creating the response object you have to pass the EventEmitter object:
var EventEmitter = require('events').EventEmitter;
var response = NodeMocks.createResponse({eventEmitter: EventEmitter});
Then, on the test, you add a listener to the event 'end' or 'send' as both of them are triggered when the call to res.send. 'end' covers more than 'send', in case you have calls other than res.send (for example, res.status(404).end().
The test would look something like this:
it('Should return the user after creation', function (done) {
auth.createUser(request, response);
response.on('send', function () {
var data = response._getData();
data.username.should.equal('someone');
data.email.should.equal('asdf2#asdf.com');
done();
});
});