In September 2025, Hieu Ngo developed comprehensive test coverage for the AsyncCounter class in the facebook/hyperion repository. He focused on validating the counter’s behavior across target counts, negative values, and promise resolution, ensuring robust handling of asynchronous logic. Using TypeScript and JavaScript, Hieu applied unit testing and asynchronous programming techniques to create a thorough suite of tests. This work did not involve bug fixes but enhanced the reliability and maintainability of Hyperion’s async components. By anchoring changes in test-driven development, Hieu reduced production risk and improved CI feedback, demonstrating depth in both testing discipline and asynchronous code quality.