What is the purpose of regression testing?

Regression testing is primarily conducted to verify that existing functionality remains intact and operates as expected after changes have been made to the software. This could include bug fixes, enhancements, or new features. The core objective is to identify any unintended consequences that these changes might introduce, ensuring that previously validated features continue to function correctly.

By focusing on maintaining the integrity of the existing application, regression testing serves as a safeguard against new defects that may emerge as a result of modifications. The process typically involves executing a suite of test cases that cover various aspects of the application's functionality that may be impacted by the changes.

In contrast, the other options focus on different testing objectives. Testing new features for marketability is a different aspect of software testing altogether, aimed at ensuring that new functionalities meet market needs. User interface assessments focus specifically on how users interact with the software, which is a subset of usability testing. Evaluating system performance under peak load pertains to performance testing, where the goal is to understand how the system behaves under extreme conditions, rather than ensuring existing functionalities are preserved.