Testing - lesson 5 | HackIndia Skills

Testing - lesson 5 | HackIndia Skills | HackIndia

Example

Express example

This example uses Node.js, Express, Jest, and Supertest. The route is small, but the pattern works for bigger apps too.

Notice that app.js exports the app. It does not call listen. That makes the test fast and avoids port conflicts on your laptop or in CI.

// app.js
const express = require('express');

const app = express();
app.use(express.json());

const expenses = [];

app.post('/expenses', (req, res) => {
  const { title, amount } = req.body;

  if (!title || typeof amount !== 'number') {
    return res.status(400).json({ error: 'title and amount are required' });
  }

  const expense = { id: expenses.length + 1, title, amount };
  expenses.push(expense);

  return res.status(201).json(expense);
});

module.exports = app;

// server.js
const app = require('./app');
app.listen(3000, () => console.log('Server running on port 3000'));

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

test('creates an expense', async () => {
  const response = await request(app)
    .post('/expenses')
    .send({ title: 'chai for team', amount: 120 });

  expect(response.status).toBe(201);
  expect(response.body).toMatchObject({
    id: 1,
    title: 'chai for team',
    amount: 120
  });
});

test('rejects an invalid expense', async () => {
  const response = await request(app)
    .post('/expenses')
    .send({ title: 'chai for team' });

  expect(response.status).toBe(400);
  expect(response.body.error).toBe('title and amount are required');
});

Test an API endpoint

One useful API test

What to check

Set up the route

Express example

Use AI carefully

Avoid weak tests

Do this now

Quick check