Why testing APIs matters in Express - See It in Action

Why Testing APIs Matters

📖 Scenario: You are building a simple Express API for a small online store. You want to make sure your API works correctly before letting customers use it.

🎯 Goal: Learn how to set up a basic Express API and understand why testing each API endpoint is important to catch errors early and ensure smooth user experience.

📋 What You'll Learn

Create a basic Express server with one GET endpoint

Add a configuration variable for the port number

Implement the main API route that returns a fixed product list

Add a final line to start the server listening on the configured port

💡 Why This Matters

🌍 Real World

APIs are the backbone of modern web apps. Testing them ensures users get correct data and smooth experiences.

💼 Career

Backend developers must build and test APIs to create reliable services that frontend apps and clients depend on.

1

Set up Express and create a basic server

Create a constant called express that requires the 'express' module. Then create a constant called app by calling express().

Express

const express = require('express');
const app = express();
// Your code here

Need a hint?

Use require('express') to import Express and call it to create your app.

2

Add a configuration variable for the port

Create a constant called PORT and set it to 3000.

Express

const express = require('express');
const app = express();
const PORT = 3000;
// Your code here

Need a hint?

Set PORT to 3000 so your server knows which port to listen on.

3

Create a GET endpoint to return products

Use app.get with the path '/products' and a callback with parameters req and res. Inside the callback, send a JSON response with an array of two products: { id: 1, name: 'Book' } and { id: 2, name: 'Pen' }.

Express

const express = require('express');
const app = express();
const PORT = 3000;

// Your code here

Need a hint?

Use app.get to create a route and res.json to send the product list.

4

Start the server listening on the port

Call app.listen with PORT and a callback function that logs 'Server running on port 3000'.

Express

const express = require('express');
const app = express();
const PORT = 3000;

app.get('/products', (req, res) => {
  res.json([
    { id: 1, name: 'Book' },
    { id: 2, name: 'Pen' }
  ]);
});

// Your code here

Need a hint?

Use app.listen to start your server and log a message when ready.