Testing the DailyNews Backend with Jest and SuperTest

The DailyNews backend ships with a suite of automated tests written with Jest and SuperTest. The tests are split into four files that collectively cover the full request lifecycle — from HTTP routing through the service layer down to individual scraper parsers. No real network calls or database connections are made during testing: the MongoDB layer and the fetch API are fully mocked, so the suite runs entirely in-process and offline.

Test Structure

feedController.test.ts

Integration tests that mount the real Express app and fire HTTP requests via SuperTest. Mocks FeedService entirely so no database or scraping logic runs.

FeedService.test.ts

Unit tests for every public method on FeedService. Both FeedRepositoryInterface and ScrapperService are replaced with jest.fn() mocks.

ElPaisScrapperRepository.test.ts

Unit tests for the El País scraper. global.fetch is replaced with a Jest mock that returns hand-crafted HTML fixtures to verify CSS selector targeting.

ElMundoScrapperRepository.test.ts

Unit tests for the El Mundo scraper. Same fetch-mocking pattern, with a dedicated fixture for articles missing a href to verify that link-less entries are skipped.

Running Tests

npm run test

Example output when all tests pass:

 PASS  src/tests/ElMundoScrapperRepository.test.ts
 PASS  src/tests/ElPaisScrapperRepository.test.ts
 PASS  src/tests/FeedService.test.ts
 PASS  src/tests/feedController.test.ts

Test Suites: 4 passed, 4 total
Tests:       22 passed, 22 total
Snapshots:   0 total
Time:        ~3s

Jest Configuration

The project uses ts-jest so TypeScript source is compiled on-the-fly without a separate build step. Tests are discovered by matching **/tests/**/*.test.ts — i.e., any .test.ts file inside a tests/ directory anywhere in the tree.

module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  testMatch: ['**/tests/**/*.test.ts'],
};

Unit Test Example

The FeedService.test.ts file demonstrates the standard mocking pattern used across the test suite. FeedRepositoryInterface is mocked with jest.fn() on every method, and ScrapperService is module-mocked at the top level so that ScrapperService.prototype.getTopNews can be controlled per-test.

import { FeedService } from '../application/services/FeedService';
import { FeedRepositoryInterface } from '../infrastructure/repositories/feed/FeedRepositoryInterface';
import { ScrapperRepositoryInterface } from '../infrastructure/repositories/scrapper/ScrapperRepositoryInterface';
import { ScrapperService } from '../application/services/ScrapperService';
import { Feed } from '../domain/model/Feed';

jest.mock('../application/services/ScrapperService');

describe('FeedService', () => {
  let feedService: FeedService;
  let feedRepository: jest.Mocked<FeedRepositoryInterface>;
  let scrappers: jest.Mocked<ScrapperRepositoryInterface>[];

  beforeEach(() => {
    feedRepository = {
      findAll: jest.fn(),
      create: jest.fn(),
      findById: jest.fn(),
      update: jest.fn(),
      delete: jest.fn(),
      saveScrappedFeeds: jest.fn(),
    } as any;

    scrappers = [{ getTopNews: jest.fn() }];
    feedService = new FeedService(feedRepository, scrappers);
  });

  describe('getAllFeeds', () => {
    it('should scrap feeds and save them', async () => {
      const scrappedFeeds = [{ title: 'Test Feed' } as Feed];
      (ScrapperService.prototype.getTopNews as jest.Mock).mockResolvedValue(
        scrappedFeeds
      );
      feedRepository.findAll.mockResolvedValue(scrappedFeeds);

      const result = await feedService.getAllFeeds();

      expect(ScrapperService.prototype.getTopNews).toHaveBeenCalled();
      expect(feedRepository.saveScrappedFeeds).toHaveBeenCalledWith(
        scrappedFeeds
      );
      expect(feedRepository.findAll).toHaveBeenCalled();
      expect(result).toEqual(scrappedFeeds);
    });
  });

  describe('getFeedById', () => {
    it('should return null if feed not found', async () => {
      feedRepository.findById.mockResolvedValue(null);

      const result = await feedService.getFeedById('1');

      expect(feedRepository.findById).toHaveBeenCalledWith('1');
      expect(result).toBeNull();
    });
  });
});

Integration Test Example

feedController.test.ts uses SuperTest to send real HTTP requests against the Express app instance. FeedService is mocked at the module level so the tests exercise routing, request parsing, and response formatting without touching the database or network.

import request from 'supertest';
import {
  SERVER_CODES,
  SERVER_MESSAGES,
  SERVER_STATUS,
} from '../api/apiConstants';
import { Feed } from '../domain/model/Feed';
import app from '../app';

let feedsMock: Feed[] = [];
let feedMock: Feed | null = {} as Feed;

jest.mock('../application/services/FeedService', () => {
  return {
    FeedService: jest.fn().mockImplementation(() => {
      return {
        getAllFeeds: () => feedsMock,
        getFeedById: () => feedMock,
        createFeed: () => ({ ...feedMock, id: '1' }),
        updateFeed: () => feedMock,
        deleteFeed: () => feedMock,
      };
    }),
  };
});

describe('FeedController', () => {
  beforeEach(() => {
    jest.clearAllMocks();
  });

  describe('getAllFeeds', () => {
    it('should return all feeds', async () => {
      feedsMock = [
        { title: 'Test Feed' } as Feed,
        { title: 'Test Feed 2' } as Feed,
      ];

      const response = await request(app)
        .get('/feed')
        .expect(200, { data: feedsMock, error: null });

      expect(response.status).toBe(SERVER_CODES.REQUEST_SUCCESSFUL);
      expect(response.body.data).toEqual(feedsMock);
    });
  });

  describe('getFeed', () => {
    it('should return 404 if feed not found', async () => {
      feedMock = null;

      const response = await request(app)
        .get('/feed/1')
        .expect(404, {
          data: null,
          error: {
            message: SERVER_MESSAGES.NOT_FOUND,
            code: SERVER_STATUS.NOT_FOUND,
          },
        });

      expect(response.status).toBe(SERVER_CODES.NOT_FOUND);
    });
  });

  describe('createFeed', () => {
    it('should return 400 if missing required fields', async () => {
      feedMock = { title: 'New Feed' } as Feed;

      const response = await request(app)
        .post('/feed')
        .send(feedMock)
        .expect(400, {
          data: null,
          error: {
            message: SERVER_MESSAGES.BAD_REQUEST,
            code: SERVER_STATUS.BAD_REQUEST,
          },
        });

      expect(response.status).toBe(SERVER_CODES.BAD_REQUEST);
    });
  });
});

Coverage

The four test files collectively verify the following:

feedController.test.ts — HTTP routing and response shapes

GET /feed returns 200 with { data: Feed[], error: null }
GET /feed/:id returns 200 with the matched feed, or 404 when getFeedById returns null
POST /feed returns 200 with the created feed, or 400 when title or link is missing from the body
PUT /feed/:id returns 200 with the updated feed, or 404 when updateFeed returns null
DELETE /feed/:id returns 204 on success, or 404 when deleteFeed returns null
Any unregistered route returns 404

FeedService.test.ts — service orchestration

getAllFeeds calls ScrapperService.getTopNews, passes the results to saveScrappedFeeds, and then calls findAll
createFeed calls feedRepository.create with the correct payload
getFeedById delegates to findById and propagates null when the feed does not exist
updateFeed delegates to repository.update and propagates null for missing IDs
deleteFeed delegates to repository.delete and propagates null for missing IDs

ElPaisScrapperRepository.test.ts — scraper parsing

getTopNews correctly extracts title, description, author, link, portrait, and newsletter from a mock HTML page containing <article> elements with El País’s CSS class structure
Returns an empty array when the HTML contains no <article> elements

ElMundoScrapperRepository.test.ts — scraper parsing

getTopNews correctly extracts all fields from El Mundo’s CSS class structure (ue-c-cover-content__byline-name, ue-c-cover-content__footer, ue-c-cover-content__image)
Skips articles where header a[href] is empty, returning an empty array for a page containing only link-less articles

To run only a specific test file without executing the full suite, use Jest’s --testPathPattern flag with any substring of the file name:

npx jest --testPathPattern=ElPais
npx jest --testPathPattern=FeedService
npx jest --testPathPattern=feedController

You can also use --watch mode during development to re-run matching tests automatically on every file save:

npx jest --watch --testPathPattern=FeedService

Getting Started

Backend

Frontend

Deployment

Testing the DailyNews Backend with Jest and SuperTest

Test Structure

feedController.test.ts

FeedService.test.ts

ElPaisScrapperRepository.test.ts

ElMundoScrapperRepository.test.ts

Running Tests

Jest Configuration

Unit Test Example

Integration Test Example

Coverage

Build docs developers (and LLMs) love

Getting Started

Backend

Frontend

Deployment

Documentation Index

​Test Structure

feedController.test.ts

FeedService.test.ts

ElPaisScrapperRepository.test.ts

ElMundoScrapperRepository.test.ts

​Running Tests

​Jest Configuration

​Unit Test Example

​Integration Test Example

​Coverage

Build docs developers (and LLMs) love

Test Structure

Running Tests

Jest Configuration

Unit Test Example

Integration Test Example

Coverage