Model instance creation assistance

[Czechh]

Hello, I'm giving a try to td and so far I really enjoy it! But I've encountered a halt when I'm trying to create an instance of an mongoose object. I want to test the userCreate and for that I've tried several approaches and all have failed.

The function to be tested:

UserController.prototype.createUser = function createUser (req, res, next) {
  //`User` is a mongoose Model (just an object with a contructor and some instance methods)
  let user = new User({
    name: req.body.name,
    username: req.body.username,
    email: req.body.email
  });

  return Promise.resolve(user.save())
    .then((newUser) => {
      return res.send(newUser);
    })
    .catch(err => {
      next(Boom.wrap(err));
    })
};

So my initial approach is:

it('creates user', (done) => {
      let userBody = {
        name: 'test-name',
        username: 'test-username',
        email: 'test-email'
      };

      let mockRequest = { body: userBody };
      const userInstance = new UserModel({ userBody })

      var user = td.object(userInstance);
      td.replace(UserModel.prototype, 'save');

      td.when(user.save())
        .thenReturn(Promise.resolve(userBody))

      var mockResponse = {
          send: td.function()
      };

      td.when(mockResponse.send(userBody))
          .thenDo(() => done());

      controller.createUser(mockRequest, mockResponse);
    });

But done() is never called, so my next try involves trying to replace the class with no success. I found an Issue regarding constructors, but haven't been able to work this out. Is there a better way to approach objects as such?

[Czechh]

Another try:

it('creates user', (done) => {
      let userBody = {
        name: 'test-name',
        username: 'test-username',
        email: 'test-email'
      };

      let mockRequest = { body: userBody };

      const user = new UserModel(userBody);

      const constructor = td.object(UserModel);;

      td.when(constructor({userBody}))
        .thenReturn(user)

      td.replace(user, 'save');

      td.when(Promise.resolve(user.save()))
        .thenReturn(userBody)

      var mockResponse = {
          send: td.function()
      };

      td.when(mockResponse.send(userBody))
          .thenDo(() => done());

      controller.createUser(mockRequest, mockResponse);
    });

But with no success, I'm getting now TypeError: Cannot read property 'scope' of undefined, that tracks with a stack:

      at model.get (node_modules/mongoose/lib/document.js:1757:38)
      at node_modules/testdouble/lib/object.js:58:47
      at arrayReduce (node_modules/lodash/_arrayReduce.js:21:19)
      at Object.reduce (node_modules/lodash/reduce.js:48:10)
      at createTestDoublesForPrototype (node_modules/testdouble/lib/object.js:57:14)
      at createTestDoubleObject (node_modules/testdouble/lib/object.js:34:14)
      at Object.module.exports [as object] (node_modules/testdouble/lib/object.js:25:18)
      at Context.<anonymous> (test/unit/controllers/user.test.js:83:30)

So I'm not mocking the object properly. I'm going to keep trying and post my development if I can make it work.

I hope it's ok for me to post here since I'm new with testing.

[Czechh]

My approach was wrong, and I switched to dependency injection and some tests are now going through, but the problem still exists with the contructor. My function is now a little different:

UserController.prototype.createUser = function createUser (req, res, next) {
  const { username, name, email } = req.body;

  return Promise.resolve(this.User({ username, name, email }))
    .then(user => user.save())
    .then(newUser => res.send(newUser))
    .catch(err => {
      console.log(err);
      next(Boom.wrap(err))
    })
};

And I'm able to mock different REST controller function except this one. I'm trying:

it('without any errors', (done) => {
      let userBody = {
        name: 'test-name',
        username: 'test-username',
        email: 'test-email'
      };

      let mockRequest = { body: userBody };

      var mockResponse = {
          send: td.function()
      };

      controller.User = td.function()

      td.when(controller.User(userBody))
        .return(Promise.resolve(userBody));

      td.when(mockResponse.send(userBody))
          .thenDo(() => done());

      controller.createUser(mockRequest, mockResponse);
    });

With no success as the console shows:

1) UserController createUser without any errors:
     TypeError: _testdouble2.default.when(...).return is not a function
      at Context.<anonymous> (__test__/unit/controllers/user.test.js:91:7)

[Czechh]

My beforeEach block include a way for other functionality to work, and they all pass

  controller = new UserController();
  controller.User = {
      findById: td.function(),
      findByIdAndUpdate: td.function(),
      save: td.function()
  };

But since I'm not sure how to mock the constructor function, I'm still reading about this.

[Czechh]

I solve this problem creating a mockModel and instantiating the controller using that mock like so:

mockModel = td.function()
mockModel.findById = td.function();
mockModel.findByIdAndUpdate = td.function();
mockModel.findByIdAndRemove = td.function();
mockModel.save = td.function();

controller = new UserController({ User: mockModel });

This way at least I have the certainty that the controller is calling those model functions correctly.

The final piece is to also create a mockUser when a user is created. And add a tesdouble function to it. => userMock = { save: td.function() }

Now the test can occur:

    it('without any errors', (done) => {
      let userBody = {
        name: 'test-name',
        username: 'test-username',
        email: 'test-email'
      };

      let mockRequest = { body: userBody };

      var mockResponse = {
          send: td.function()
      };

      // New User created from mockModel
      let mockUser = {
        save: td.function()
      }

      td.when(controller.User(userBody))
        .thenReturn(Promise.resolve(mockUser));

      td.when(mockUser.save())
        .thenReturn(Promise.resolve(userBody))

      td.when(mockResponse.send(userBody))
          .thenDo(() => done());

      controller.createUser(mockRequest, mockResponse);
    });

I'm learning about this as I go, I hope it is not spamming the team developing this tool.