What is the focus of regression testing?

Regression testing primarily aims to verify that recent changes or enhancements in a software application do not adversely impact its existing functionalities. This is crucial after software maintenance activities, such as bug fixes, upgrades, or modifications, to ensure that previously working features remain functional. By running regression tests, developers and testers can identify any unintended side effects caused by the new code.

While introducing new features, evaluating performance under stress, and modifying system components are important aspects of software development and quality assurance, they do not specifically align with the primary goal of regression testing, which centers on maintaining the integrity of existing functionalities. Therefore, ensuring that existing functionality is unaffected by maintenance efforts is the correct emphasis of regression testing.