Worked on stabilizing the test suite for the vercel/vercel CLI, focusing on eliminating fixture-related flakiness to improve continuous integration reliability. Addressed issues with terminal hyperlink rendering by aligning mock reset behavior with terminal capabilities, ensuring tests run consistently across different environments. Improved fixture hygiene by cleaning up temporary files created during deploymentId validation tests, preventing pollution that could affect subsequent runs. Enhanced validation and test plans for vitest CLI tests to ensure predictable outcomes. Utilized JavaScript and TypeScript for CLI development, file system management, and mocking, resulting in reduced flaky CI outcomes and strengthened core CLI quality across platforms.