Agentic Code Review & Regression Testing

GridCraft is a browser-based pixel-art editor that allows users to create, edit, import, and export pixel artwork. While the original application was functional, its development workflow relied heavily on manual verification and had no automated regression test infrastructure. Our project uses IBM Bob to transform this existing codebase into a more reliable and testable application through an agentic software-engineering workflow. Bob first analyzes the repository and identifies correctness issues, defensive programming gaps, configuration problems, and opportunities to improve testability. The workflow then implements targeted fixes across the application. These include correcting the export workflow, improving theme and keyboard shortcut behavior, preventing unintended preview-mode changes, adding defensive checks for browser and Canvas APIs, and improving export concurrency and cleanup. An existing flood-fill algorithm was also refactored from App.jsx into a standalone utility. This separates algorithmic logic from React state and allows the functionality to be tested independently. The project introduces Vitest, React Testing Library, jsdom, and V8 coverage reporting. Regression tests cover flood fill, theme switching, undo/redo, export, keyboard shortcuts, grid-size behavior, image import/export, and defensive browser behavior. The resulting workflow follows an agentic cycle of repository understanding, issue discovery, planning, implementation, testing, and verification. This demonstrates how IBM Bob can be used not only to generate code, but also to improve an existing project systematically and establish a repeatable engineering workflow.