Differentiate between Functional and Non-Functional Testing

Functional Testing:

• Definition: Tests what the system does (features and functions)
• Focus: Verify functionality against requirements
• Question: “Does it work as expected?”
• Based On: Functional requirements/specifications
• Testing Type: Black box testing
• Examples:
  • Unit Testing
  • Integration Testing
  • System Testing
  • UAT
  • Smoke Testing
  • Sanity Testing
  • Regression Testing

Non-Functional Testing:

• Definition: Tests how well the system performs (quality attributes)
• Focus: Verify performance, usability, reliability
• Question: “How well does it work?”
• Based On: Non-functional requirements (performance, security, etc.)
• Testing Type: Can be black box or white box
• Examples:
  • Performance Testing
  • Load Testing
  • Stress Testing
  • Security Testing
  • Usability Testing
  • Compatibility Testing
  • Scalability Testing
  • Reliability Testing

Key Differences

Aspect	Functional	Non-Functional
Tests	What system does	How system performs
Execution	Before non-functional	After functional
Manual Testing	Easy to perform	Difficult manually