Testing
SvelteKit ships without a testing setup. You create a project with npm create svelte@latest, pick a template, and get a working app — but zero tests. This guide covers everything you need: unit tests for utilities, component tests for Svelte components, integration tests for load functions and API routes, and
Testing
Playwright is the E2E test runner of choice for SvelteKit. It drives a real browser — Chromium, Firefox, or WebKit — against your running app. Unlike Vitest component tests that run in jsdom, Playwright tests exercise real browser behavior: navigation, cookies, local storage, JavaScript rendering, and network requests. This guide covers Playwright
Testing
SvelteKit API routes (+server.ts) and server load functions (+page.server.ts) contain your application's backend logic. They handle request validation, database queries, authentication checks, and error responses. Testing them directly — without starting a server — is fast, reliable, and catches the class of bugs that frontend tests completely
Testing
SvelteKit form actions handle POST requests from <form> elements on the server. They validate input, interact with databases, send emails, and return structured responses. Testing them directly — without a running server — catches validation bugs, missing error handling, and incorrect redirects before they reach users. How Form Actions Work
Testing
Svelte stores hold application state. When store logic is wrong — a derived value computes incorrectly, a custom store doesn't clean up subscriptions, an async store gets stuck in a loading state — components using that store will fail in ways that are hard to trace. Testing stores in isolation
Testing
Svelte components have logic in them. Props control rendering, user interactions trigger state changes, events propagate to parent components. Testing that logic prevents regressions and documents expected behavior. This guide covers Svelte component testing with Vitest and @testing-library/svelte — the combination used by most production SvelteKit projects in 2026.
Test Automation
SvelteKit gives you fast builds and a clean full-stack model. It also ships with no testing setup at all. You add a route, it works in the browser, and you move on — until it breaks in a way that would have taken two minutes to catch with a test.