Difference Between Functional Testing and Non-Functional Testing in STLC

Functional testing and non-functional testing are two essential types of testing in the Software Testing Life Cycle (STLC).

Functional Testing:

Functional testing focuses on verifying that the software application functions correctly as per the specified requirements. It involves testing the individual functions of the software to ensure they perform as expected.

Non-Functional Testing:

Non-functional testing, on the other hand, evaluates the performance, usability, reliability, and other non-functional aspects of the software. It tests how well the system performs under various conditions and stresses.

Main Differences:

1. Functional testing checks the specific functions of the software, while non-functional testing evaluates the overall performance and characteristics of the system.
2. Functional testing is concerned with what the system does (the features), while non-functional testing focuses on how well it does it (performance, usability, etc.).
3. Functional testing is black-box testing, while non-functional testing can involve both black-box and white-box testing techniques.
4. Functional testing is usually carried out earlier in the testing process, whereas non-functional testing is often performed after functional testing.

Overall, both functional and non-functional testing are crucial in ensuring the quality and reliability of the software product during the STLC.