Focus on maintainability and reliability, not just coverage. An unmaintainable framework becomes technical debt faster than production code.
Strong answers mention: Page Object Model, data-driven testing, config-driven test environments, reporting and logging, CI integration, parallel execution, retry mechanisms for flaky tests, and clear separation between test logic and test data. Best candidates discuss maintainability as the primary design goal.
Tests technical depth. Ask to see code examples or describe their framework architecture. Red flag: frameworks that only they can maintain. Good sign: well-documented, team-adopted frameworks.