React Testing

What you'll learn

• Why Testing Library asks you to test what the user sees
• The query priority order, and why getByTestId is last resort
• When userEvent is closer to reality than fireEvent
• How findBy and waitFor handle UI that arrives over time
• What deserves a mock — network, modules — and what doesn't
• When a renderHook test beats a component test, and when it doesn't
• What works today for testing Server Components, and what doesn't
• How to spot flaky waitFor, overspecified assertions, and unread snapshots

1. 01
   Why test from the outside

   Testing Library's doctrine. Test what the user sees, not what the component owns.
   13 min
2. 02
   render and queries

   getByRole, getByLabelText, the priority order. Why getByTestId is the last resort.
   16 min
3. 03
   userEvent vs fireEvent

   Clicks, typing, tabbing. Why userEvent simulates a real user and fireEvent does not.
   14 min
4. 04
   Async UI

   findBy, waitFor, and the rules for testing things that arrive over time.
   15 min
5. 05
   Mocking

   Mock the network, sometimes the module. Don't mock your own components or hooks.
   14 min
6. 06
   Testing custom hooks

   renderHook for hooks without UI. When a hook test beats a component test, and when it loses.
   13 min
7. 07
   Testing Server Components, today

   What works for RSC tests in 2026, what doesn't, and where the seams actually are.
   13 min
8. 08
   Test smells and recovery

   Flaky waitFor, overspecified assertions, snapshots that nobody reads. How to undo each one.
   12 min