According to the ISTQB Glossary, regression testing is required for what purpose?

Regression testing is primarily conducted to ensure that recent changes or modifications to the software have not introduced new defects or adversely affected existing functionalities. When a software modification occurs, such as bug fixes, enhancements, or changes in configuration, there is a risk that these changes could unintentionally disrupt the previously working features.

The process of regression testing specifically aims to identify any new issues that may have arisen as a result of these modifications, ensuring that the overall integrity and performance of the software remain intact. This is crucial in maintaining system reliability and confidence in ongoing development practices because it verifies that previously passed test cases still yield the expected results after changes have been made.

By focusing on ensuring that modifications do not introduce defects, regression testing plays a vital role in the software development lifecycle, especially in areas such as continuous integration and iterative development models, where software changes are frequent and ongoing.