Emphasise user-centric testing: "I use React Testing Library with getByRole queries, test what the user sees and does, and mock API calls with MSW to test realistic flows."
Best practice: test behaviour, not implementation. Use React Testing Library to render components and interact with them as a user would. Unit test custom hooks in isolation. Integration test key user flows. Avoid testing implementation details like internal state or DOM structure. Strong candidates mention accessibility queries (getByRole, getByLabelText) and mock APIs at the network level (MSW).
Tests professional frontend practices. Candidates who test implementation details (checking state values, counting renders) are writing brittle tests. Those who use RTL idiomatically and focus on behaviour are strong.