Testing React Server Components: Vitest Strategies for Async Boundaries and Mocking (2026)

React Server Components (RSC) are revolutionizing how applications render by executing as async functions on the server, not the client. Testing them requires a nuanced approach, and this tutorial guides you through building a robust testing strategy. We'll explore the three-tier approach, Vitest environment configuration, rendering async server components, mocking boundaries, testing suspense boundaries, and the integration vs. E2E test decision heuristic. By the end, you'll have a comprehensive understanding of how to effectively test RSCs, ensuring your applications are both functional and reliable.