React Testing in 2026: Vitest, React Testing Library and Best Practices
Master React testing with Vitest and React Testing Library. Learn component testing patterns, async handling, mocking strategies, and interview-ready best practices for 2026.
React / Next.js
FRONTEND
Modern frontend development combining React as UI library with Next.js as full-stack framework. Architecture based on Server Components, App Router, Server Actions, and hybrid rendering (SSR, SSG, ISR) for production-ready applications.
What you'll learn
Modern React with Server Components, Suspense and advanced hooks (useActionState, use)
Next.js App Router with layouts, streaming SSR and partial prerendering
Server Actions for server-side mutations without API routes
Strict TypeScript with type inference and type safety
File-based routing with dynamic routes and route groups
Modern data fetching (fetch with cache, Server Components, parallel data)
State management (Context API, Zustand, TanStack Query for server cache)
Styling with TailwindCSS, CSS Modules, styled-components or Sass
Comprehensive testing (Vitest/Jest, React Testing Library, Playwright/Cypress)
Performance (Image/Font optimization, code splitting, lazy loading, analytics)
Key topics to master
The most important concepts to understand this technology and ace your interviews
1
React: JSX, Virtual DOM, reconciliation, fiber architecture
2
Modern hooks: useState, useEffect, useContext, useMemo, useCallback, useActionState
3
Server Components vs Client Components ("use client"), composition patterns
4
Props, State, lifting state up, prop drilling and solutions
5
React lifecycle, useEffect cleanup, dependency array, strict mode
6
Next.js App Router: routing, layouts, templates, loading/error states
7
Data fetching: async Server Components, fetch caching, revalidation strategies
8
Server Actions: progressive enhancement, useActionState, form handling
9
Rendering strategies: SSR, SSG, ISR, client-side, streaming
10
State management: Context API, Zustand, Redux Toolkit, server state (TanStack Query)
11
Performance: React.memo, useMemo, useCallback, lazy loading, Suspense boundaries
12
Routing: dynamic routes, parallel routes, intercepting routes, middleware
13
Metadata and SEO: generateMetadata, sitemap, robots.txt, Open Graph
14
Testing: component tests, integration tests, E2E, mocking, test patterns
15
Build optimization, bundle analysis, deployment (Vercel, Docker), monitoring
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