Regression testing

IEC 62304 expects regression testing after every change, scaled to the change and its risk. Skipping it is a common audit finding for software updates.

the testing required to determine that a change to a SYSTEM component has not adversely affected functionality, reliability or performance and has not introduced additional defects [ISO/IEC 90003:2004, definition 3.11]

IEC 62304:2006+AMD1:2015, clause 3.15