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Jest SpyOn - Actual Method is Called, Instead of the Mocked Implementation

I've searched high and low to try and get my Jest test to work but have gotten nowhere in my search.
I've got a function (createRoom) that I want to unit test and I want to mock a method (gameFactory.createNewGameWithInitialPlayer()) call.
GameService.ts
const GameService = (games: {[index: string]: Game}) => {
const playerFactory = PlayerFactory()
const gameFactory = new GameFactory()
const createRoom = ({name, device, socketID}: {name: string, device: string, socketID: string}): RoomResponse => {
const player = playerFactory.createNewPlayer(name, device, socketID)
if (player && player.id) {
const game: Game|undefined = gameFactory.createNewGameWithInitialPlayer(player)
...
}
...
}
GameFactory.ts
export class GameFactory {
createNewGameWithInitialPlayer = (player: Player): Game|undefined => {
const game = new Game()
game.spectators[player.id as any as number] = player
return game
}
}
GameService.test.ts
import * as gameFactory from '../Factories/GameFactory'
describe('Testing Game Service', () => {
test('createRoom', () => {
jest.spyOn(gameFactory, 'GameFactory').mockReturnValue({ createNewGameWithInitialPlayer: jest.fn().mockReturnValue(undefined)})
const response: RoomResponse = gameService.createRoom({
name: 'Player 1',
device: DevicesEnum.ios,
socketID: 'some-socket-id'
})
...
}
...
}
In GameService.test.ts I am mocking the return value of the createNewGameWithInitialPlayer method call. However, when I run the test, the actual implementation of it runs, instead of my mocked version. For this test in particular, I want the createNewGameWithInitialPlayer method to return undefined, but that does not happen, it appears to be calling the actual method implementation.

If you want to override the createNewGameWithInitialPlayer and return what you want then, you have to mock the import of GameFactory class in your test.
// Here you are creating your mock and saying the default return Game object
const mockCreateNewGameWithInitialPlayer = jest.fn().mockImplementation(() => new Game());
// Here you say to jest that any file who wants to import "GameFactory"
// will import this fake class
jest.mock('rootofGameFactory/GameFactory', () => ({
GameFactory: function(){
return {
// and when any file wants to execute this method, will execute my mock
createNewGameWithInitialPlayer: mockCreateNewGameWithInitialPlayer
}
}
}))
describe('Testing Game Service', () => {
test('createRoom', () => {
const response: RoomResponse = gameService.createRoom({
name: 'Player 1',
device: DevicesEnum.ios,
socketID: 'some-socket-id'
})
...
}
...
}
If you want to change the return object of your mocked method, you have to do it like this...
test('createRoom 2', () => {
//Here you say to jest, just ONCE (for this test) return an instance of Game2
mockCreateNewGameWithInitialPlayer.mockImplementationOnce(() => new Game2())
const response: RoomResponse = gameService.createRoom({
name: 'Player 1',
device: DevicesEnum.ios,
socketID: 'some-socket-id'
})
...
}

The jest documentation mentions
By default, jest.spyOn also calls the spied method. This is different behavior from most other test libraries. If you want to overwrite the original function, you can use jest.spyOn(object, methodName).mockImplementation(() => customImplementation) or jest.replaceProperty(object, methodName, jest.fn(() => customImplementation));
So you could do something like
jest.spyOn(gameFactory, 'GameFactory').mockImplementation(() => { return undefined })

Mocking html-pdf using Jest

I am using the html-pdf package in my nodejs code (not in Typescript). Now, this package has a create() function which is chained with the toBuffer() function. I am unit testing my code using Jest and want to mock this call pdf.create(html).toBuffer().
var pdf = require('html-pdf');
pdf.create(html).toBuffer(function(htmlToPdfError, buffer){
if (htmlToPdfError) {
reject(htmlToPdfError);
}
resolve(buffer.toString('base64'));
});
EDIT:
I am trying to use the following code in my spec file to make the module:
jest.mock('html-pdf', () => ({
create: jest.fn(() => {
return Promise.resolve();
})
}));
This is helping me mock the create() function but I do not know how to return a object in Promise.resolve which would have a toBuffer function

I could mock it using the following code:
const mockToBuffer = {
toBuffer: jest.fn((callback: Function) => callback(null, null)),
}
jest.mock('html-pdf', () => ({
create: jest.fn(() => mockToBuffer),
}))
it('Should work', async () => {
const expectedResult = Buffer.from([10])
mockToBuffer.toBuffer.mockImplementation((callback: Function) => {
callback(null, expectedResult)
})
// const result = await yourFuncUsingHtmlPdf(/* fakePayload */)
// Comparing the buffer using the native function
// expect(expectedResult.equals(result)).toBe(true)
}

will this work?
and then assert that your "pdf" buffer contains "test string"?
jest.mock('html-pdf', () => ({
create: jest.fn(() => {
return Promise.resolve({
toBuffer: function(callback) {
callback(null, Buffer.from("test string", "utf-8"));
},
});
})
}));
(I haven't tried it)

Mock sequelize with Jest and sequelize-mock

I'm building a new project and I'm trying to use TDD as my default methodology and trying to apply it with integration test.
The thing is easy I want to retrieve all the users from my DB.
//controller.js
const UserService = require('../services/user');
module.exports = {
// corresponds to /users
getAllUsers: async (req, res, next) => {
const users = await UserService.fetchAllUsers();
res.send(users);
},
};
const models = require('../database/models/index'); // I tried also with destructuring
module.exports = {
fetchAllUsers: async () => models.user.findAll(),
};
and my actual test file looks like
const request = require('supertest');
const SequelizeMock = require('sequelize-mock');
const app = require('..');
const dbMock = new SequelizeMock();
const models = require('../src/database/models/index');
jest.mock('../src/database/models/index', () => ({
user: jest.fn(),
}));
models.user.mockImplementation(() => {
const UserMock = dbMock.define('user', {});
UserMock.$queueResult(UserMock.build({
username: 'username',
mail: 'myMail#myMail.com',
}));
return UserMock;
});
describe('Demo test', () => {
it('should respond to users route', (done) => {
request(app)
.get('/users')
.end((err, res) => {
expect(err).toBeNull();
expect(res.status).toBe(200);
expect(res.json).toBe('object');
done();
});
});
});
All of this is actually working but when I'm trying to mock the user I TypeError: models.user.findAll is not a function
I need to replace the model.user with the UserMock's value.
Is there anyway to do this? or I should just mock findAll like
jest.mock('../src/database/models/index', () => ({
user: () => ({ findAll: jest.fn() }),
}));
``

In this case, I was not mocking what I wanted to.
If you wish to mock the models all you need to do is use SpyOn
like
const { sequelize, Report, User } = require('../../database/models/index');
describe("my test", () => {
it("should just mock", () => {
jest.SpyOn(Report, "count").mockResolvedOnce(6);
})
})
In the case that you need to mock like your service
first create jest functions to allow the access from outside the scope of your mock
and then mock it with "double class call"
const BaseService = require('../BaseService');
const mockFecthOne = jest.fn();
jest.mock('../BaseService',
() => jest.fn().mockImplementation(
() => ({
fetchOne: mockFetchOne,
}),
));
// inside your test just
BaseService().fetchOne.mockResolvedOnce({....})
and thats it hope it works.

Is it possible to mock API calls with Jest in NodeJS without jest.mock('module')?

My NodeJS application has to do some API requests, so I'm mocking their return as my tests are just for my application's business logic. However, there's two things that I quite didn't understand.
I'm using jest's mockImplementation method to change the return of my service, but I can't make it work without calling jest.mock with the service beforehand.
Also, if I try to set automock: true in my jest.config.js, it returns me an error:|
TypeError: Cannot set property 'gracefulify' of undefined
Here's my test.js code in where I'm testing a function that calls automation.js, which has my application logic and make the calls for my services:
const automation = require('../automations/fake.automation');
// MOCKS
const mockedBlingProduct = require('../mocks/bling-product.mocks.json');
const mockedShopifyCreatedProduct = require('../mocks/shopify-created-product.mocks.json');
// SERVICES
const BlingProductService = require('../services/bling-product.service');
const ShopifyProductService = require('../services/shopify-product.service');
jest.mock('../services/bling-product.service');
jest.mock('../services/shopify-product.service');
describe('Automation test', () => {
beforeEach(() => {
const blingMockedReturn = jest.fn(() => {
return mockedBlingProduct;
});
const shopifyMockedReturn = jest.fn(() => {
return mockedShopifyCreatedProduct;
});
BlingProductService.mockImplementation(() => {
return {
list: blingMockedReturn
};
});
ShopifyProductService.mockImplementation(() => {
return {
create: shopifyMockedReturn
};
});
});
it('should return status SUCCESS', async () => {
const result = await
.run();
expect(result).toEqual({ status: 'SUCCESS' });
});
});
And here's the code of one of my services, keep in mind that the logic behind the API calls is abstracted from the service. In the mockImplementation I'm trying to overwrite the list and create functions inside them:
class BlingPriceService {
async list(query = {}) {
const httpMethod = 'GET';
const resource = 'produtos/page={pageNumber}/json';
const options = {
queryString: query,
urlParams: {
pageNumber: 1,
}
};
return blingComponent.request(httpMethod, resource, options);
}
}
module.exports = BlingPriceService;

const automation = require('../automations/fake.automation');
// MOCKS
const mockedBlingProduct = require('../mocks/bling-product.mocks.json');
const mockedShopifyCreatedProduct = require('../mocks/shopify-created-product.mocks.json');
// SERVICES
const BlingProductService = require('../services/bling-product.service');
const ShopifyProductService = require('../services/shopify-product.service');
describe('Automation test', () => {
beforeAll(() => {
jest.spyOn(BlingProductService.prototype, 'list').mockImplementation(() => Promise.resolve(mockedBlingProduct));
jest.spyOn(ShopifyProductService.prototype, 'list').mockImplementation(() => Promise.resolve(mockedShopifyCreatedProduct));
});
afterAll(() => {
jest.restoreAllMocks();
});
it('should return status SUCCESS', async () => {
const result = await automation.run();
expect(result).toEqual({ status: 'SUCCESS' });
});
});

js jest mock classes and static methods

I wrote mock for my class and everything works, when I test creating instance, but not, when I test static method. How to fix this?
Here is my testing class:
class Order {
async add(items) {
const order = new OrderModel({items});
await order.save();
//...
}
async find(items) {
const query = OrderModel.find({
//condition
});
//...
}
}
My OrderModel mock:
const mockOrderModel = {
save: jest.fn(),
find: jest.fn(),
exec: jest.fn()
};
jest.mock('../order/order.model', () => {
return jest.fn().mockImplementation(() => {
return {
save: mockOrderModel.save,
find: mockOrderModel.find,
exec: mockOrderModel.exec
};
});
});
And tests for both methods:
//WORKS
it('add()', async () => {
await order.add(['']);
expect(OrderModel).toHaveBeenCalledTimes(1);
expect(mockOrderModel.save).toHaveBeenCalledTimes(1);
});
//NOT WORKS
it('find()', async () => {
await order.find(['']);
expect(mockOrderModel.find).toHaveBeenCalledTImes(1);
});
OrderModel.find() method is not called

That's because find on mockOrderModel is defined as a property of an object and not a static method. So basically you're creating a mock object for Order with find property that must be called on an instance. Static method of Order is not mocked. To do so you can try:
Order.find = jest.fn()