Top QA Engineer Interview Questions & Answers

Functional testing — Does the feature work correctly? • Unit testing (individual functions) • Integration testing (module interactions) • System testing (complete application) • User acceptance testing (UAT — business requirements) • Regression testing (existing features still work after changes) Non-functional testing — How well does the feature perform? • Performance testing — Response time under normal load • Load testing — Behavior under expected peak load • Stress testing — Behavior beyond capacity limits • Security testing — Vulnerability scanning, penetration testing • Accessibility testing — WCAG compliance, screen reader compatibility • Usability testing — User experience evaluation Key insight: Both are equally important. A feature that works correctly but crashes under load isn't production-ready.

Automate when: • Tests need to run frequently (regression suites) • The feature is stable (not changing rapidly) • The test is deterministic (same input → same output) • High risk of human error in manual execution • Data-driven testing with many input combinations Keep manual when: • Exploratory testing (discovering unexpected bugs) • UI/UX subjective evaluation • One-time or rarely-run tests • Features still being designed (automation would be wasted) • Accessibility testing that requires human judgment ROI formula: Automation ROI = (Manual effort × Number of runs) - (Automation development + Maintenance effort) Practical rule: If a test will run more than 5 times, automate it. If the feature changes weekly, wait until it stabilizes.