Explain your reasoning for each test level. "I unit test business logic, integration test API contracts, and E2E test the critical user journey" shows strategic thinking.
Strong answers reference the testing pyramid: many unit tests, fewer integration tests, minimal E2E tests. They should discuss risk-based testing (critical paths need more coverage), testing boundaries and edge cases, and knowing when not to test (trivial getters, framework code). Best candidates mention test maintenance cost.
Tests practical judgment. Candidates who write no tests are risky. Candidates who test everything waste time. Look for the balance and the reasoning behind it.