Hands-On Introduction to Testing with Jest

Name: Hands-On Introduction to Testing with Jest
Rating: 4.8 (12 reviews)

Guide to testing JavaScript and TypeScript apps with Jest from scratch

Created byLukasz Kallas

Last updated 8/2026

English

English [Auto],

What you'll learn

Understand what testing is and why it's important in software development
Install and configure Jest in JavaScript and TypeScript projects
Write unit tests for functions and modules using Jest
Use Jest matchers and assertions to verify code behaviour
Test asynchronous code including promises and async/await
Work with mocks and spies to isolate code under test

Course content

3 sections • 20 lectures • 4h 43m total length

Welcome!3:04
This hands-on course teaches you to write tests with Jest in VS Code, covering matchers, assertions, asynchronous code, mocking, setup and teardown, and code coverage.
Join Our Community0:04
What is Jest & Why to Use it7:53
Setup7:19
Set up your Jest testing environment by installing Node.js and VS Code, verify versions, and prepare extensions to streamline JavaScript testing.
Project10:51
set up a practice project for Jest after installing Node.js and VS Code, install dependencies with npm install, and explore src utilities, validators, and services to prepare for writing tests.

Installation14:04
Install and configure Jest for a TypeScript project, adding ts-jest, types/jest, and Jest globals as dev dependencies, generate a TypeScript Jest config, and run the first test to verify setup.
First Tests16:21
Write real Jest tests for math utilities, testing add with different inputs and divide error handling. Master test structure, toThrow assertions, and patterns like file naming and watch mode.
Matchers20:34
Learn how to use Jest matchers to write precise assertions with toBe vs toEqual, truthiness, toContain, toHaveLength, numeric comparisons, regex matches, floating point tolerance, and negations.
Testing15:42
Develop and run comprehensive tests for pure string utilities using Jest, covering capitalize, reverse string, is palindrome, and truncate, with TypeScript type checks and edge-case scenarios.
Describe9:23
Group tests with describe blocks in Jest to organize output, nest blocks for isPalindrome and other functions, and learn concise test naming and it usage for clear, scalable test suites.
Async Code25:25
Test asynchronous code with Jest by validating promise-based API calls like fetch user and save data, ensuring proper handling with returns, resolves, and rejects.
async/await Syntax22:42
Learn to write clean jest tests with async/await, including fetch post tests and resolves/rejects matchers. Use beforeEach and afterEach for database tests.
Error Handling20:26
Learn how to test error handling with Jest by validating synchronous and asynchronous error cases, including toThrow, regex, error instances, and rejects, with examples like divide, factorial, and database.
Mocking23:14
Learn how to mock in Jest by using mock functions to replace dependencies, control what it returns, verify calls, and test asynchronous behavior.
Modules Mock25:11
Master module mocking in Jest by replacing a module's exports with mocks, control return values with mockResolvedValue, and reset mocks between tests; build partial mocks with a factory and requireActual.
Spies18:59
Hooks19:22
Explore Jest hooks for reliable tests, including beforeAll, afterAll, beforeEach, and afterEach, to set up and tear down a database and ensure a clean slate across tests.
TypeScript18:45

Requirements

Basic JavaScript knowledge including functions, objects, arrays, and ES6 syntax
Familiarity with Node.js and npm
Basic understanding of asynchronous JavaScript (promises and async/await)
Basic TypeScript knowledge is helpful but not required

Description

This hands-on course provides a practical introduction to testing JavaScript and TypeScript applications using Jest, one of the most popular testing frameworks in the JavaScript ecosystem.

If you’ve ever wanted to write reliable tests, catch bugs earlier, and build more confidence in your code, this course is for you.

We focus on learning by doing. There are no theory-heavy slides or long explanations. Instead, you’ll start writing real tests from the very first lessons and build practical skills that you can immediately use in your own projects.

You’ll begin by setting up Jest in a project and understanding how the testing workflow works. From there, we’ll cover unit testing for functions and modules, working with assertions and matchers, and understanding how to read test results.

As the course progresses, you’ll learn how to test asynchronous code using promises and async/await, use mocks and spies to isolate dependencies, and write cleaner, more maintainable test suites.

We’ll also cover testing TypeScript code, handling edge cases, organizing tests properly, and debugging failing tests effectively.

Throughout the course, you’ll work with practical examples based on real-world coding scenarios, helping you understand not just how to write tests, but why they matter.

By the end of this course, you’ll feel confident using Jest in your daily workflow and adding automated testing to both small and large projects.

This course is a great fit if you are:

A beginner developer learning professional coding practices
A JavaScript or TypeScript developer who wants to start testing
A backend or frontend developer improving code quality
Anyone who wants to ship more reliable applications

If you want a clear, beginner-friendly, and hands-on introduction to testing with Jest, this course is for you.

Who this course is for:

JavaScript and TypeScript developers who want to learn testing
Frontend and backend developers looking to improve code quality
Anyone who wants to understand how to write and run tests with Jest

Hands-On Introduction to Testing with Jest

What you'll learn

Explore related topics

Course content

Welcome & Setup5 lectures • 29min

Jest Basics13 lectures • 4hr 10min

Ending2 lectures • 4min

Requirements

Description

Who this course is for: