How to get Start with Jest

Table of Contents

1. Introduction
2. Init NPM repo and setup packages
3. Add test Script at package.json
4. Add Javascript and Test
5. Run the npm run test

Introduction

This blog shows how to get start quickly to test with JavaScript.

Init NPM repo and setup packages

Here we will setup the npm repo, then later install the dependencies package jest.

npm init -y

npm install --save-dev jest

Add test Script at package.json

Add test command with jest, now if we run npm run test, should run jest with default setting.

  "scripts": {
    "test": "jest"
  },

Add Javascript and Test

Here, create a file and create few JavaScript functions.

function sum(a, b) {
    return a + b;
}

function exponent(a,b) {
    return a ** b;
}

function subtraction(a, b) {
    return a -b;
}
module.exports = {
    sum,
    subtraction,
    exponent
};

Next, create test file and add test code.

const {exponent, subtraction, sum} = require('../src/sample');

test('test sum', () => {
    expect(sum(1, 2)).toBe(3);
});

test('test subtraction', () => {
    expect(subtraction(10, 2)).toBe(8);
});

test('test exponent', () => {
    expect(exponent(5, 2)).toBe(25);
});

Run the npm run test

That's it, now we can see the test passed.