Developed unit-test mocks for LocalApicLib within the microsoft/mu_basecore repository, focusing on enhancing testability and code safety. The work involved creating MockLocalApicLib.h and MockLocalApicLib.cpp as test doubles for LocalApicLib.h, allowing for isolated unit testing without modifying production code or affecting existing functionality. This approach leveraged C++ and low-level programming techniques, along with mocking frameworks and unit testing patterns, to enable more reliable regression protection and faster CI feedback. The implementation maintained backward compatibility, introducing no breaking changes or security impacts, and provided a foundation for safer refactoring and improved confidence in future code modifications.