Migrating 6000 React tests using AI Agents and ASTs (eliocapella.com)

A developer at Filestage successfully migrated over 6000 test cases from React Testing Library v13 to v14 using AI agents and Abstract Syntax Trees (ASTs). Initially relying on Claude Code CLI for the migration, the developer encountered numerous test failures due to substantial changes in the new version, such as the requirement for asynchronous APIs and altered timing behaviors. Recognizing the challenges, they crafted a migration guide and utilized jscodeshift to create a codemod that efficiently transformed test files, facilitating a structured, incremental migration across multiple pull requests (PRs). This migration project highlights the potential of AI in coding maintenance tasks, particularly in managing extensive legacy codebases. By employing AST manipulation and iterative improvements to the migration process, the developer minimized manual debugging time and maintained high test coverage, achieving a remarkable balance between automation and oversight. Notably, the process reinforced best practices in software development, emphasizing the need for careful validation and iterative adjustments, thereby potentially revolutionizing how developers approach routine migrations and maintenance tasks, freeing them to focus on more complex customer-centric challenges.