Mocking modules in Node.js for unit testing

Question

I want to unit test some functions in a node.js module. I think that mocking a 3rd module would be helpful. In particular to avoid hitting the database

# models/account.coffee
register = (email, password)->
   sha_sum.update(password)
   pw = sha_sum.digest('hex')
   user = 
      email: email
      password: sha_sum.digest('hex')

   users_db.save user, (err, doc)->
      register_callback(err)

account_module = 
   register: register

module.exports = account_module

This is the module that i want to test

# routes/auth.coffee
account = require '../models/account'

exports.auth = 
   post_signup: (req, res)->
      email = req.body.email
      password = req.body.password
      if email and password
          account.register(email, password)
          res.send 200
      else
          res.send 400

I want to be able to test that hitting this url with the correct body in the post calls the account.register function but i don't want the test to hit the database. I may not have implemented the account module yet.

The jasmine spec # specs/auth.test.coffee describe 'signup', ->

   request = require 'request' 
   it 'should signup a user with username and password', (done)->

       spyOn(account, 'register') # this does not work, account.register still called
       url = root + '/signup'
       headers =
           "Content-Type": "application/json" 
       data = 
           email: '[email protected]'
           password: 'pw'
       body = JSON.stringify(data)
       request {url: url, method: 'POST',json: data, headers: headers }, (err, response, body)->

           expect(response.statusCode).toEqual(200)
           done()

I have looked into several mocking libraries for node.js (https://github.com/easternbloc/Syringe, https://github.com/felixge/node-sandboxed-module) but so far no success. Whatever i try in the spec, the account.register always get executed. Is this whole approach flawed?

Answer 1

I am using mocha as the test framework and sinon for mocking, stubing and spying. I would suggest you delegate your account module to the auth.coffee module and mock it like so:

exports.init = function (account) {
    // set account object
}

so from the mocha test you can then create a dummy account object and mock it with sinon in the actual test.

describe('some tests', function () {

    var account, response, testObject;

    beforeEach(function () {

        account = {
             register: function () { }
        };

        response = {
            send: function () { }
        };

        testObject = require('./auth');
        testObject.init(account);
    });

    it('should test something', function () {

        var req = { body: { email: ..., password: .... } }, // the request to test
            resMock = sinon.mock(response),
            registerStub = sinon.stub(account, 'register');

        // the request expectations
        resMock.expect('send').once().withArgs(200);

        // the stub for the register method to have some process
        registerStub.once().withArgs('someargs');

        testObject.auth(req. response);

        resMock.verify();

    });

});

Sorry for not writing it down in coffescript but I am not used to it.