What is Non-functional testing?

Non-functional testing verifies the non-functional requirements of a software system rather than end-user features.

While functional specifications dictate what the software should do, non-functional specifications determine how the system should be.

Non-functional testing evaluates aspects like performance, security, usability, compliance, etc., depending on the application under test.

Non-functional testing includes:

  • Compliance testing: testing whether the software complies with the laws.
  • Documentation testing: verifying that the documentation is accurate, complete, and integrated with the application.
  • Reliability testing: checking whether the system performs as expected when used for the specified period.
  • Performance testing: ensuring that when many users use the system, it is performant and runs without errors.
  • Localization and internationalization testing: checks whether the software behaves as expected when used in different countries, languages, time zones, currencies, etc.
  • Recovery testing: tests how well the software recovers from hardware and software errors.
  • Security testing: examines the system's security elements like confidentiality, authentication, authorization, and integrity.
  • Usability testing: checks how well end-users can use the product.

Why is Non-functional Testing Important?

Non-functional testing is as necessary as functional testing because it is closely linked to customer satisfaction. If the application had a good feature set but is slow, has lousy documentation, security holes, or some other non-functional issues, the customer will lose confidence and eventually stop using the application.