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Functional Testing Vs Non-Functional Testing


The Software Development process, generally emphasizes on the functional requirements of the software product. However, non-functional requirements are also needs to be considered, from user-perspective, of using the software product, in an unexpected situation and environment.

Functional testing is a testing techniques, which evaluates the functional requirements and aspects that were decided, prior to the development phase, whereas non-functional testing concerns with the non-functional requirements.

To make it clear, the concept of functional and non-functional testing, we have to go through the differences, between them, as under:

SNO. Functional Testing Non-Functional Testing
1. Evaluates the functional requirements/ functionality of the software product. Examines the non-functional traits and aspects of the software product.
2. The functional requirements, are identified, specified and decided, prior to the development process. Non-functional requirements, are generally not specified, but are hypothetical, based on the users-perspective.
3. The chief purpose behind functional testing is to ensure the fulfilment of the functional requirements, in the developed product. The key reason, to perform non-functional testing, is to evaluate the software product ability, to meet the customer’s unforeseen needs and expectations in an unexpected circumstances.
4. Based on business or client's requirement. Depends upon the end-user's expectations.
5. Validates the software behaviour. Certifies the software performance.
6. It encompasses following testing activities:
  • White Box Testing
  • Black Box Testing
  • Unit Testing
  • Integration Testing
  • Smoke Testing
  • Usability Testing
  • System Testing
  • Regression Testing
  • Globalization Testing
  • User Acceptance Testing
  • Localization Testing
  • Interface Testing
The testing techniques, covered under it, are
  • Availability Testing
  • Compatibility testing
  • Load Testing
  • Endurance Testing
  • Localization and Internationalization Testing
  • Performance Testing
  • Maintainability Testing
  • Recovery Testing
  • Configuration Testing
  • Compliance testing
  • Installation Testing
  • Documentation
  • Security Testing
  • Reliability Testing
  • Volume Testing
  • Scalability Testing
  • Usability Testing
  • Stress Testing
7. Responsible for the accurate, desired and proper working of the each functionality of the software product. Concerns with the performance of the software product.
8. It is first priority of the testers. It may be performed, after the execution of the functional tests.
9. Manual testing is considered best for its execution. Automated testing, is an effective approach, for the execution of non-functional test cases, using automation tools.
10. Time-Consuming activity. Less-time consuming process.