Testing GET endpoints in Express - Mini Project: Build & Apply

Testing GET endpoints

📖 Scenario: You are building a simple Express server that has a GET endpoint to return a list of books. You want to write tests to make sure this endpoint works correctly.

🎯 Goal: Create a basic Express app with a GET endpoint at /books that returns a list of books. Then write a test using a testing library to check that the endpoint returns the correct data and status code.

📋 What You'll Learn

Create an Express app with a GET endpoint /books

The endpoint should return a JSON array of book objects

Write a test that sends a GET request to /books

The test should check that the response status is 200

The test should check that the response body matches the expected books array

💡 Why This Matters

🌍 Real World

Testing GET endpoints is essential for backend APIs to ensure they return the correct data and status codes before deploying to production.

💼 Career

Backend developers and QA engineers often write tests like these to maintain API quality and prevent bugs.

1

Create the books data array

Create a constant array called books with these exact objects: { id: 1, title: '1984' } and { id: 2, title: 'Brave New World' }.

Express

// Create the books array with two book objects
// Your code here

Need a hint?

Use const books = [ ... ] to create the array with two objects inside.

2

Set up the Express app and import modules

Import express and create an app variable called app by calling express().

Express

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' }
];

// Import express and create app
// Your code here

Need a hint?

Use const express = require('express') and const app = express().

3

Create the GET endpoint for /books

Use app.get with path '/books' and a callback with parameters req and res. Inside the callback, send the books array as JSON using res.json(books).

Express

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' }
];

const express = require('express');
const app = express();

// Create GET /books endpoint
// Your code here

Need a hint?

Use app.get('/books', (req, res) => { res.json(books); }).

4

Write a test for the GET /books endpoint

Import supertest and use it to create a request object with supertest(app). Write a test named 'GET /books returns books list' that sends a GET request to /books and expects status 200 and the JSON body to equal the books array.

Express

const books = [
  { id: 1, title: '1984' },
  { id: 2, title: 'Brave New World' }
];

const express = require('express');
const app = express();

app.get('/books', (req, res) => {
  res.json(books);
});

// Import supertest and write test for GET /books
// Your code here

Need a hint?

Use supertest to send a GET request and check status and body with expect.