Worked on improving test reliability for the NomicFoundation/hardhat repository by addressing a critical issue in the test harness. Focused on stabilizing asynchronous contract function calls to prevent transaction leaks, ensuring that each contract function settled fully before any ABI checks or assertions were performed. This approach reduced test flakiness and improved the consistency of continuous integration runs. Utilized JavaScript and TypeScript to implement robust error propagation, rethrowing transaction errors only after ABI checks passed. The work centered on smart contract development and testing, emphasizing careful async handling to maintain test isolation and integrity across the codebase during the development cycle.