Supertest for HTTP assertions in Express - Mini Project: Build & Apply

Supertest for HTTP assertions

📖 Scenario: You are building a simple web server using Express. You want to check that your server responds correctly to HTTP requests. This is like testing if a vending machine gives you the right snack when you press a button.

🎯 Goal: Build a small Express server and write tests using Supertest to check the server's responses. You will create the server, set up Supertest, write a test for the home page, and finally add a test for a JSON response.

📋 What You'll Learn

Create an Express app with a GET route at '/' that returns 'Hello World!'

Set up Supertest to test the Express app

Write a test that checks the '/' route returns status 200 and text 'Hello World!'

Add a GET route at '/data' that returns JSON { message: 'Hello JSON' }

Write a test that checks the '/data' route returns status 200 and the correct JSON

💡 Why This Matters

🌍 Real World

Testing web servers ensures they respond correctly before users see them. This prevents bugs and improves reliability.

💼 Career

Backend developers often write tests with Supertest to verify APIs work as expected, which is a key skill in web development jobs.

1

Create Express app with '/' route

Create an Express app in a variable called app. Add a GET route at '/' that sends the text 'Hello World!' as the response.

Express

// Your code here

Need a hint?

Use express() to create the app. Use app.get to add the route. Use res.send to send the text.

2

Set up Supertest for the app

Import supertest and create a variable called request by calling supertest(app). This will let you test the app's routes.

Express

import express from 'express';
const app = express();
app.get('/', (req, res) => {
  res.send('Hello World!');
});

// Your code here

Need a hint?

Import Supertest and call it with app to create request.

3

Write a test for '/' route

Write an async test function called testHomeRoute. Inside, use await request.get('/') to get the response. Check that response.status is 200 and response.text is 'Hello World!'.

Express

import express from 'express';
import supertest from 'supertest';
const app = express();
app.get('/', (req, res) => {
  res.send('Hello World!');
});
const request = supertest(app);

// Your code here

Need a hint?

Use await request.get('/') to get the response. Check response.status and response.text with if statements.

4

Add '/data' route and test JSON response

Add a GET route at '/data' that sends JSON { message: 'Hello JSON' }. Then add an async test function called testDataRoute. Use await request.get('/data') and check that response.status is 200 and response.body.message is 'Hello JSON'.

Express

import express from 'express';
import supertest from 'supertest';
const app = express();
app.get('/', (req, res) => {
  res.send('Hello World!');
});

// Your code here

const request = supertest(app);

async function testHomeRoute() {
  const response = await request.get('/');
  if (response.status !== 200) throw new Error('Status is not 200');
  if (response.text !== 'Hello World!') throw new Error('Text is not Hello World!');
}

// Your code here

Need a hint?

Add the route with app.get and send JSON with res.json. Write the test like the first one but check response.body.message.