Worked on the microsoft/STL repository to enhance the reliability and maintainability of the C++ Standard Library test suite. Focused on cleaning up legacy MSVC-specific workarounds in ranges iterator tests, simplifying conditional compilation and aligning tests with current compiler behavior. Addressed pointer interconvertibility trait tests by removing non-standard layout cases, ensuring accurate deduction for standard-layout types and reducing flaky test results. Utilized C++, the C++ Standard Library, and advanced metaprogramming techniques to improve test readability and CI stability. These targeted bug fixes lowered regression risk, optimized CI resource usage, and reinforced the long-term maintainability of the STL codebase.