Be specific: "I unit test service classes with mocked repositories, integration test repositories against a real test database, and use data providers for edge cases."
Strong answers describe a testing pyramid: many unit tests for business logic, fewer integration tests for database/API interactions, and minimal end-to-end tests. Candidates should mention mocking dependencies, test databases, data providers, and code coverage as a guide (not a target). Best answers discuss testing strategies for specific patterns like repositories, services, and controllers.
Tests professional development practices. Developers without testing experience or who only write trivial tests are a risk for code quality. Ask about a bug they caught through testing.