How do I test React components without relying on implementation details?

Use React Testing Library queries that reflect how users interact with the UI, such as getByRole, getByLabelText, and getByText.

How can I mock API requests in React tests with Mock Service Worker?

Configure Mock Service Worker handlers to intercept Fetch or Axios requests and return controlled responses without calling a real API.

What is the best way to unit test Next.js useRouter in Jest?

Mock the next/router module and provide the route values and router methods your component needs for each test case.

Free Course Image React.js Unit Testing and Integration Testing Tutorial

Free online course React.js Unit Testing and Integration Testing Tutorial

Duration of the online course: 3 hours and 36 minutes

New

Build reliable React apps with this free course on unit & integration testing using Jest and React Testing Library, plus mocks, async tests, and CI tips.

In this free course, learn about

Core testing concepts: unit vs integration, test pyramid, and confidence-focused testing
Write refactor-resilient React tests by focusing on user behavior, not implementation details
Set up a React testing stack: Jest, React Testing Library, ESLint, TypeScript, and GitHub Actions CI
Understand when and why to use custom Jest + ts-jest instead of default setups
Use React Testing Library basics: render, screen, and userEvent for realistic interactions
Prefer accessible queries (getByRole, getByLabelText) over test IDs to improve resilience
Test async UI: waiting for updates, handling promises, and asserting loading/error states
Mock functions and components with Jest: spies, mocks, and module mocking patterns
Mock HTTP calls with MSW for fetch/axios to test network-driven UIs reliably
Test SWR hooks/components: caching, revalidation, and server states using MSW
Test React forms: input changes, validation messages, and submission flows
Unit test Next.js routing by mocking useRouter and asserting navigation behavior

About the free online course

High-quality React applications don’t happen by accident. They come from confidence: knowing a refactor won’t silently break key user flows, knowing your components behave correctly when data is slow, and knowing releases won’t be derailed by last-minute bugs. This free online course helps you build that confidence by teaching practical unit and integration testing for React.js with an emphasis on tests that are resilient, readable, and focused on real user behavior.

You’ll start by grounding yourself in testing concepts so you can choose the right kind of test for each situation and understand what makes a test valuable. From there, you’ll learn how to set up a modern React testing environment with Jest and React Testing Library, enforce consistent code quality with linting, and connect your test suite to automated checks in CI so problems are caught before they reach production.

A major focus is learning how to test components the way users experience them, avoiding fragile tests that depend on implementation details. You’ll practice using recommended querying patterns that naturally encourage accessible UI, and you’ll become comfortable writing asynchronous tests that handle delayed rendering, loading states, and state updates without flakiness.

Real-world apps also depend on external pieces, so the course shows how to mock components and functions with Jest and how to simulate network behavior with tools designed for realistic HTTP mocking. You’ll learn approaches for testing data-fetching scenarios, including components powered by popular hooks, and you’ll see how to validate form behavior with clear, maintainable assertions.

Finally, you’ll strengthen your toolbox by testing routing-related logic in a Next.js context, giving you patterns you can reuse across products that rely on navigation and route state. By the end, you’ll be equipped to design tests that support refactoring, improve reliability, and speed up development through safer, faster feedback loops.

Course content

Video class: Introduction to Testing: Concepts for Beginners - React.js Testing Tutorial #1 12m
Exercise: What is the recommended approach to make React component tests more resilient to refactors?
Video class: Setup Testing Env: Jest, React Testing Library, eslint, GitHub Actions -React.js Testing Tutorial #2 32m
Exercise: Why use a custom Jest + ts-jest setup instead of relying on the default testing setup?
Video class: React Testing Library for Beginners: React.js Testing Tutorial #3 36m
Exercise: In React Testing Library, which querying approach is recommended to avoid relying on implementation details and improve accessibility-focused tests?

Video class: React Async Testing using React Testing Library for Beginners: React.js Testing Tutorial #4 22m
Video class: Mocking React Components and Functions using Jest for Beginners - React.js Testing Tutorial #5 26m
Video class: Mock HTTP calls using Fetch or Axios - Mock Service Worker - React.js Testing Tutorial #6 28m

Video class: React Hooks SWR: Test components that useSWR - Mock Service Worker - React.js Testing Tutorial #7 12m
Video class: Testing React Forms - React Testing Library - React.js Testing Tutorial #8 31m
Video class: Unit Testing Next.js Router - useRouter - React.js Testing Tutorial #9 14m

Learn aboutReact JS

Explore the best free online React JS courses and learn to build fast, interactive web applications with hands-on lessons for beginners and aspiring developers. Study React components, hooks, state, props, routing, and modern front-end development at your own pace. Enroll today for free training and earn a certificate to showcase your React JS skills.

Learn aboutJavaScript

Explore the best free online JavaScript courses with certificates and build in-demand web development skills at your own pace. Learn JavaScript fundamentals, DOM manipulation, ES6, APIs, frameworks, and more through beginner-friendly and advanced classes. Enroll today, earn a certificate, and strengthen your resume for developer career opportunities.