Automate TypeScript Architecture Rules with ArchUnitTS to Prevent Code Decay

Software teams following Clean or Hexagonal Architecture often see their layering rules quietly broken under deadline pressure, with controllers importing repositories and domain models pulling in framework decorators. These violations go unnoticed because the rules live only in documentation and code reviews, not in automated checks. Architecture testing libraries like ArchUnitTS allow developers to write automated tests that validate structural rules — such as dependency direction between layers and naming conventions — rather than business logic. If any rule is violated, the build fails immediately, removing the need for manual review to catch structural drift. Integrating such tests into a NestJS or similar TypeScript project requires minimal setup and can enforce conventions that would otherwise be forgotten in a Notion document.