Chong Ren Lee enhanced the test infrastructure for the LifeSG/web-frontend-engine repository by addressing a reliability gap in the unit testing process. He migrated the test runner from using focused tests with 'fit' to standard tests with 'it', ensuring that all tests execute by default and eliminating the risk of hidden focused tests passing unnoticed in both CI and local environments. This adjustment, implemented in JavaScript and TypeScript, focused solely on the test suite and did not alter production code. The work demonstrated a methodical approach to improving test coverage and reliability, reflecting depth in frontend development and unit testing practices.