Integration Testing with Supertest

Introduction

While unit tests focus on isolated functions, Integration Testing verifies that multiple components of your Express application work together correctly. This typically involves booting up the server, hitting the endpoints, and ensuring that the database or third-party APIs interact as expected.

Setting Up a Test Database

You should never run integration tests against your production database. Instead, use a dedicated test database that is seeded and cleared before each test run.

If you are using MongoDB and Mongoose, you can use mongodb-memory-server for lightning-fast, isolated database tests.

Using Supertest

Like unit testing, supertest is the industry standard for sending HTTP requests to your Express app during tests.

const request = require('supertest');
const app = require('../app');
const mongoose = require('mongoose');

beforeAll(async () => {
  // Connect to the test database
  await mongoose.connect('mongodb://localhost:27017/test_db');
});

afterAll(async () => {
  // Clean up and disconnect
  await mongoose.connection.dropDatabase();
  await mongoose.connection.close();
});

describe('User API', () => {
  it('should create a new user', async () => {
    const response = await request(app)
      .post('/api/users')
      .send({ name: 'Alice', email: 'alice@example.com' });
      
    expect(response.status).toBe(201);
    expect(response.body.name).toBe('Alice');
    
    // Verify the database state
    const user = await mongoose.model('User').findOne({ email: 'alice@example.com' });
    expect(user).toBeTruthy();
  });
});

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