What method can be used to verify that new code changes do not adversely affect existing system functionalities?

Using a regression test is essential for verifying that new code changes do not negatively impact existing functionalities within a system. The primary focus of regression testing is to ensure that recent updates, enhancements, or bug fixes have not introduced any new faults in previously functioning features.

When code changes are made, they can inadvertently affect existing code due to interdependencies or shared components. Regression testing involves re-running a suite of previously conducted tests against the modified codebase to check for any discrepancies in functionality, performance, or security issues that may arise due to the changes. This process ensures that while new features are introduced or existing ones modified, the integrity of the system remains intact, thus confirming that no unintended side effects have occurred.

Although integration tests, acceptance tests, and unit tests also play significant roles in the software development life cycle, they serve different purposes. Integration tests focus on verifying interaction between combined units of code, acceptance tests validate the system against business requirements, and unit tests check the functionality of individual components in isolation. However, only regression tests explicitly target the validation of existing features in light of new changes, making it the most appropriate method in this scenario.