What type of testing ensures that previous functionalities remain intact after changes in code?

Regression testing is specifically designed to verify that recent changes or updates to the code have not adversely affected the existing functionalities of the software. After code modifications, such as bug fixes, enhancements, or any other changes, regression testing is performed to ensure that all previously working features still function as intended. It checks for unintended side effects and helps maintain software stability over time.

This type of testing is critical in any development cycle, especially when dealing with iterative improvements or updates, as it helps catch defects early and ensures that quality is maintained throughout the project life cycle.

The other types of testing mentioned serve different purposes: Smoke testing is a basic check to see if the major functions of an application work, performance testing evaluates how the software performs under various conditions, and stress testing determines the application's behavior under extreme conditions. These do not focus on maintaining functionality after code changes like regression testing does.