Testing - lesson 3 | HackIndia Skills

Testing - lesson 3 | HackIndia Skills | HackIndia

Example

Same feature, two tests

Say your hackathon app splits a food bill for friends after a canteen order. The calculation is unit-test material. The HTTP endpoint that accepts the bill and returns the split is integration-test material.

This example uses JavaScript with Jest and Supertest. The exact framework can change. The choice stays the same.

// bill.js
function splitBill(totalRupees, people) {
  if (people <= 0) throw new Error('people must be positive');
  return Math.ceil(totalRupees / people);
}
module.exports = { splitBill };

// bill.test.js - unit test
const { splitBill } = require('./bill');

test('splits a bill and rounds up to the next rupee', () => {
  expect(splitBill(101, 4)).toBe(26);
});

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

test('POST /split returns per-person amount', async () => {
  const res = await request(app)
    .post('/split')
    .send({ totalRupees: 101, people: 4 });

  expect(res.status).toBe(200);
  expect(res.body.perPersonRupees).toBe(26);
});

Choose unit or integration

One decision

Use unit when

Use integration when

Choose the level

Same feature, two tests

Common mistake

Use AI carefully

Do this now

Quick check