Vitest (unit + integration testing)

Vitest is our default test runner for unit and lightweight integration tests.

What to test (rule of thumb)

• Unit tests: pure logic (formatters, validators, mapping functions).
• Integration tests: a small slice of components + their dependencies (mock boundaries, not internals).
• Don’t use unit tests to “prove the framework works”.

Sources

• Vitest docs: https://vitest.dev/ 
• Assertions (expect): https://vitest.dev/api/expect.html 
• Mocking: https://vitest.dev/guide/mocking.html 

If we use React Testing Library in the app, also:

• RTL docs: https://testing-library.com/docs/react-testing-library/intro/ 

Standard approach (what we’ll converge on)

• Test behavior over implementation details.
• Mock at the boundary:
  • mock tRPC client calls in UI tests
  • mock microservice/data layer in procedure tests
• Prefer factories for test data (typed helpers).

Exercises

• content/exercises/05-typescript/01-refactor-js-to-ts-with-tests.mdx
• content/exercises/06-vitest/01-component-and-boundary-tests.mdx