vitest-best-practices

The best way to structure readable Vitest unit tests is using the AAA pattern, which separates Arrange, Act, and Assert phases for consistent test organization and clarity across JavaScript and TypeScript suites.

You can write parameterized tests in Vitest using the it.each feature to run the same assertions against multiple inputs. This provides broad coverage with minimal code duplication across your test data sets.

Handle mocking and test doubles safely in Vitest by following explicit guidance on safe mocking practices. This ensures your test doubles do not leak across tests and maintain reliable, isolated execution for your unit tests.

Yes, this Vitest guidance applies to both frontend and backend JavaScript and TypeScript projects. The patterns cover general testing structures, async handling, and error handling that work across different project environments.

Refactor legacy test suites into Vitest tests by first reading the AGENTS.md file to adopt core patterns, then loading specific references to guide your refactoring. This enforces explicit assertions and standardized test structures.

General patterns for async testing in Vitest require careful error handling to avoid unhandled rejections. While these patterns standardize test suites, you must ensure explicit assertions are used to catch async errors reliably during execution.