What does non-functional system testing include?

Non-functional system testing focuses on assessing various quality attributes of a software system rather than its specific functional behavior. This type of testing examines aspects such as performance, usability, reliability, security, and scalability, which are essential for determining how well the system performs under various conditions and how user-friendly it is.

The testing of quality attributes is critical because it gives insight into the system's responsiveness and efficiency, as well as the overall user experience. For example, performance testing might involve evaluating how the system behaves under high load, while usability testing assesses how easy and intuitive it is for users to interact with the system.

Other options do not accurately reflect the purpose of non-functional testing. While testing for where a system fails or its proper functions and features is important, this pertains more to functional testing. Hence, the alignment with quality attributes distinctly validates why the correct answer is about testing these specific non-functional aspects.