Reference

https://jestjs.io/

Notes

How to set up Jest using WebPack:

https://jestjs.io/docs/getting-started

Introduction to jest-DOM

jest-dom is a companion library for Testing Library that provides custom DOM element matchers for Jest

npm install --save-dev @testing-library/jest-dom

Example of Using JEST

// sum.js

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

module.exports = sum;

// sum.test.js

const sum = require('./sum');

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

npm test