E2E testing with supertest in NestJS - Mini Project: Build & Apply

E2E Testing with Supertest in NestJS

📖 Scenario: You are building a simple NestJS application that manages a list of books. You want to ensure your API endpoints work correctly by writing end-to-end (E2E) tests using supertest. This will help catch bugs early and keep your app reliable.

🎯 Goal: Write E2E tests for the GET /books endpoint using supertest in a NestJS testing environment. You will set up the test module, configure the app, write the test to check the response, and finalize the test suite.

📋 What You'll Learn

Create a NestJS testing module with the BooksModule

Initialize the NestJS application for testing

Write a supertest test to check the GET /books endpoint returns status 200 and an empty array

Close the NestJS application after tests complete

💡 Why This Matters

🌍 Real World

E2E testing ensures your API works as expected from the user's perspective. It helps catch bugs before deployment and improves software quality.

💼 Career

Many companies require developers to write automated tests for backend APIs. Knowing how to write E2E tests with NestJS and supertest is a valuable skill for backend and full-stack roles.

1

Setup NestJS Testing Module

Import Test and TestingModule from @nestjs/testing. Create a testing module with BooksModule using Test.createTestingModule and compile it. Assign the compiled module to a variable called moduleFixture.

NestJS

# Import Test and TestingModule
# Create a testing module with BooksModule
# Compile the module and assign to moduleFixture
# Your code here

Need a hint?

Use Test.createTestingModule with imports: [BooksModule] and call compile() to get the testing module.

2

Initialize NestJS Application for Testing

Create a NestJS application instance from moduleFixture by calling createNestApplication(). Assign it to a variable called app. Then call await app.init() to initialize the app.

NestJS

import { Test, TestingModule } from '@nestjs/testing';
import { BooksModule } from '../src/books/books.module';

let moduleFixture: TestingModule;

moduleFixture = await Test.createTestingModule({
  imports: [BooksModule],
}).compile();

// Create app from moduleFixture and initialize it
// Your code here

Need a hint?

Use moduleFixture.createNestApplication() to create the app, then call await app.init().

3

Write E2E Test for GET /books Endpoint

Use supertest to send a GET request to /books on the app.getHttpServer(). Write a test that expects the response status to be 200 and the response body to be an empty array []. Use await request(app.getHttpServer()).get('/books').expect(200).expect([]).

NestJS

import { Test, TestingModule } from '@nestjs/testing';
import { BooksModule } from '../src/books/books.module';
import { INestApplication } from '@nestjs/common';
import * as request from 'supertest';

let moduleFixture: TestingModule;
let app: INestApplication;

moduleFixture = await Test.createTestingModule({
  imports: [BooksModule],
}).compile();

app = moduleFixture.createNestApplication();
await app.init();

// Write a supertest call to GET /books and expect status 200 and empty array
// Your code here

Need a hint?

Use request(app.getHttpServer()).get('/books').expect(200).expect([]) to test the endpoint.

4

Close the NestJS Application After Tests

Call await app.close() to properly shut down the NestJS application after tests finish.

NestJS

import { Test, TestingModule } from '@nestjs/testing';
import { BooksModule } from '../src/books/books.module';
import { INestApplication } from '@nestjs/common';
import * as request from 'supertest';

let moduleFixture: TestingModule;
let app: INestApplication;

moduleFixture = await Test.createTestingModule({
  imports: [BooksModule],
}).compile();

app = moduleFixture.createNestApplication();
await app.init();

await request(app.getHttpServer())
  .get('/books')
  .expect(200)
  .expect([]);

// Close the app after tests
// Your code here

Need a hint?

Call await app.close() to clean up the app after tests.