Kyungjun Lee focused on enhancing test reliability in the kafka_study repository by refactoring the test suite to ensure proper resource cleanup, particularly with Toxiproxy, after each test run. Working primarily in Java and leveraging Kafka and advanced testing techniques, Kyungjun adjusted test timeouts to more accurately simulate network failure scenarios, which reduced test flakiness and improved the determinism of CI feedback loops. Although no new features were delivered during this period, the work addressed a persistent bug and laid a solid foundation for future development by stabilizing the test environment and improving overall developer efficiency for the project.