undefined不是函数：单元测试护照身份验证自定义回调

Question

I'm new to passport and express and trying to get a better idea of how everything works together by creating unit tests for all of my code. I have been having good success but today ran into an issue I don't quite understand...

I'm attempting to unit test the following exported function on session.js :

'use strict';

var mongoose = require('mongoose'),
passport = require('passport');

exports.login = function (req, res, next) {
  passport.authenticate('local', function(err, user, info) {
    var error = err || info;
    if (error) return res.json(401, error);

    req.logIn(user, function(err) {

      if (err) return res.send(err);
      res.json(req.user.userInfo);
    });
  })(req, res, next);
};

I seem to be having trouble with the second to last line (req, res, next) and how/when it gets called. I also have never seen this type of call in Javascript where the last line is just a set of parameters.

In order to test I'm using rewire , sinon, and mocha. In my test I'm using rewire to change the passport dependency to a mock object that I control.

My test seems to be working as expected as evidenced by where it is failing and what instanbul is telling me is covered but it alwasy throws: TypeError: undefined is not a function .

If I comment out the (req, res, next) line in session.js then my test actually runs successfully.

My test session.unit.js :

'use strict';

var rewire = require('rewire'),
should = require('should'),
sinon = require('sinon'),
sessionController = rewire('../../../../lib/controllers/session'),
passportMock = {};


describe('Session Controller', function() {

  describe('#login', function(){

    beforeEach(function(){
      sessionController.__set__({
        'passport': passportMock
      });

    });

    it('should return 401 status and error if passport authentication returns error', function(){
      //given
      var res = {
          json: sinon.spy(),
          send: sinon.spy()
        },
        req = {
          logIn: sinon.spy()
        },
        next = sinon.stub();

      passportMock.authenticate = sinon.stub().callsArgWith(1, 'ERROR', null, null);

      //when
      sessionController.login(req, res, next);

      //then
      res.json.calledWith(401,'ERROR').should.be.true;
    });

  });

});

My questions are:

1. What is the last line (req, res, next) used for and when is it called? (I suspect middleware)
2. Is there a way I can change my test to get it to pass without the undefined error?

Thanks very much for reading and any help you can provide!!

** EDIT: ** I think I left out a critical piece of information... This session.login function is called from my routes.js file so I believe the last line is needed for middleware to continue. I'm still confused as to how to allow this to continue processing in the unit testing though.

routes.js snippet:

  app.route('/api/session')
    .post(session.login)
    .delete(session.logout);

** EDIT2: **

Added the top part of session.js for clarity on how passport is initially declared with require . In the unit test I am replacing passport via rewire with my mock (stub) object so that I can control what passport returns.

Answer 1

1. The })(req, res, next); towards the end of your session.js is unnecessary because of how scoping rules work in JavaScript and because passport.authenticate does not return a function (it probably returns nothing which by default returns undefined), so that is the reason for the error.

2. Just change the })(req, res, next); from the end of session.js to just }); .

Answer 2

I'm not sure if this will help, but this is generally how I stub passport.authenticate when used in the same way you have.

var stub = sinon.stub(passport, 'authenticate').returns(function() {});
stub.yields(new Error('fails here'));

// add your tests here

stub.restore();