Testing a function which consumes promises - node.js

Question

I've got a MEAN app and I'm trying to get tests to work on the node side. Async events are wrapped in promises, which are consumed in the controller. I failed at testing the controller :(
The controller I'm trying to test:
ProjectController.prototype.getAll = function(req, res, next) {
req.dic.subjectRepository
.getById(req.params.subjectId)
.then(function(subject) {
res.json(subject.projects);
}, function(err) {
return res.status(404).send('Subject does not exist.' + err);
});
};
The subjectRepository is our data source, which returns a promise (mpromise because under the hood we're using mongoose, but it shouldn't matter):
So in our test we tried mocking the request (we're injecting our dependency injection container from a middleware into the req) and response (the test succeeds if response.json() has been called with the subjects we tried to fetch) and our subjectRepository. We used bluebird (although I tried others out of frustration) to create fake promises for our mocked subjectRepository:
describe('SubjectController', function() {
'use strict';
var Promise = require('bluebird');
it('gets all existing subjects', function() {
// -------------------------------------
// subjectRepository Mock
var subjectRepository = {
getAll: function() {},
};
var subjectPromise = Promise.resolve([
{name: 'test'},
{name: 'test2'},
]);
spyOn(subjectRepository, 'getAll').andReturn(subjectPromise);
// -------------------------------------
// request mock
var req = {
dic: {
subjectRepository: subjectRepository,
},
};
// -------------------------------------
// response mock
var res = {
json: function() {},
send: function() {},
};
spyOn(res, 'json');
// -------------------------------------
// actual test
var subjectController = new (require('../../../private/controllers/SubjectController'))();
subjectController.getAll(req, res);
// this succeeds
expect(subjectRepository.getAll).toHaveBeenCalled();
// this fails
// expect(res.json).toHaveBeenCalled();
});
});
Question: How do I make the test run the expect() AFTER the promise succeeded?
Node v0.12
The code is on GitHub for anyone who's interested: https://github.com/mihaeu/fair-projects
And maybe I should mention that the controller is called from the router:
// router handles only routing
// and controller handles data between view and model (=MVC)
subjectRouter.get('/:subjectId', subjectController.get);
I got this to work by changing our controllers to hand down the promises, but I'm not sure this is what we want. Isn't there a way to get my approach to work?
it('gets all existing subjects', function(done) {
// ...
var subjectController = new (require('../../../private/controllers/SubjectController'))();
subjectController.getAll(req, res).then(function() {
expect(res.json).toHaveBeenCalledWith(testSubjects); // success
}).finally(done);
expect(subjectRepository.getAll).toHaveBeenCalled(); // success
}

Answer 1

Your code makes the mistake of mixing business logic with front facing routing.
If your getAll did not touch the request and response object, it would look something like this:
ProjectController.prototype.getAll = function(subjectId) {
return req.dic.subjectRepository.getById(subjectId).then(function(subject){
return subject.projects;
});
};
Now, it is no longer related to the request response life cycle or in charge of logic, testing it is trivial by:
it("does foo", function(){
// resolve to pass the test, reject otherwise, mocha or jasmine-as-promised
return controller.getAll(152).then(...)
});
That would make your actual handler look like:
app.get("/projects", function(req, res){
controller.getAll(req.params.subjectId).then(function(result){
res.json(result);
}, function(){
res.status(404).send("...");
});
});