How do you write unit tests in Node.js? Unit tests check small, isolated pieces of your code (like functions) to make sure they work

s expected.

Basic example using Mocha and Chai:

// calculator.js

function add(a, b) {

return a + b;
}
module.exports = add;

// test/calculator.test.js

const add = require('../calculator');
const { expect } = require('chai');

describe('add function', () => {

it('should return the sum of two numbers', () => {

const result = add(2, 3);

expect(result).to.equal(5);

});

});

Run tests with:

mocha

This test suite checks if add(2,3) equals 5 — simple and effective.