What does stress testing determine about an application?

Stress testing is a type of non-functional testing that evaluates how an application behaves under heavy load conditions. The primary goal is to determine the application's stability and reliability when subjected to extreme or excessive demands, which can simulate scenarios such as high user traffic, increased data processing, or maximum system capacity.

Through this testing, teams can uncover how the system performs under stress, identifying limitations, breaking points, and potential failure modes that could occur under such conditions. This information is crucial for ensuring that the application can handle anticipated peak loads, maintain performance levels, and provide a reliable user experience when traffic or processing demands surge.

The other choices focus on aspects that do not align with the core purpose of stress testing: user-friendliness pertains more to usability testing; error rates during normal operations relate to functional testing; and code quality and readability are critical in code reviews and static analysis, not stress testing. Thus, the primary objective of stress testing firmly ties it to assessing stability and reliability under extreme load conditions.