Worked on the Arize-ai/phoenix repository to enhance the reliability and maintainability of end-to-end UI tests. Focused on front end development using React, JavaScript, and TypeScript, the work involved introducing stable data-testid attributes to key UI buttons, refactoring markup for consistency, and documenting testing ID conventions. By decoupling test selectors from visible text and DOM structure, the changes reduced test flakiness and maintenance overhead. The approach leveraged Playwright for automation and established clear guidelines for testing IDs, resulting in faster CI feedback, safer UI evolution, and improved onboarding for new contributors through disciplined use of data-* attributes and documentation.