Yoni Kaplan developed a CLI Test Plan Missing Files Warning System for the tuist/tuist repository, focusing on improving developer feedback and reliability during test planning. Using Swift and leveraging CLI development and error handling skills, Yoni implemented a mechanism that alerts users when required xctestplan files are absent, addressing a common source of ambiguous test results and failed CI runs. The solution integrates directly into the test plan workflow, providing actionable warnings that help developers quickly identify configuration issues. This targeted feature enhanced the predictability of test executions and streamlined debugging, reflecting a thoughtful approach to developer experience and workflow reliability.