Testing
Next.js has built-in i18n routing, but testing it is non-trivial. The routing behavior depends on request headers, cookies, the next.config.js configuration, and your chosen URL strategy. This guide covers unit testing locale-aware pages, integration testing routing logic, and end-to-end Playwright tests that
Testing
NextAuth.js v5 (now called Auth.js) is a significant rewrite that embraces Next.js App Router and Edge runtime. Testing Auth.js v5 apps is different from v4 — there's no more getServerSideProps, sessions are handled via auth() from the server, and the middleware approach changed. This guide
Test Automation
Partial Prerendering (PPR) is Next.js 15's hybrid rendering strategy: the static shell of a page is served instantly from the CDN edge, while dynamic content streams in behind Suspense boundaries. A single page can have both a prerendered header and a live-fetched product listing — without a
Test Automation
Next.js 15 App Router introduced a file-based convention that determines how your application behaves in loading, error, and layout states. Each file — layout.tsx, loading.tsx, error.tsx, not-found.tsx — plays a distinct role, and each one needs tests that match its purpose. This guide covers how
Testing
tRPC's createCaller() lets you call router procedures directly in tests — no HTTP server, no fetch mocking, no supertest. You inject the context (auth session, database client) yourself, which means you can test authenticated and unauthenticated flows, input validation, middleware enforcement, and error handling with plain function calls. This
Test Automation
Next.js gives you a lot out of the box: routing, server components, API routes, middleware, server actions. Each of those layers can break in ways that only show up in production if you don't have tests covering them. This guide covers the full testing stack for a