Stress testing is a type of performance testing that evaluates how a system behaves under extreme load conditions, such as high user traffic, large data volumes, or limited resources. It is useful for identifying potential bottlenecks, errors, or failures that may affect the system's functionality or availability. Stress testing during the quality assurance (QA) phase would have identified the concern of users complaining that a newly released ERP system is functioning too slowly. The other options are not as relevant for this concern, as they relate to different aspects of testing, such as regression testing (verifying that existing functionality is not affected by new changes), interface testing (verifying that the system interacts correctly with other systems or components), or integration testing (verifying that the system works as a whole after combining different modules or units). References: CISA Review Manual (Digital Version), Domain 5: Protection of Information Assets, Section 5.4 Testing Techniques1