Unit Testing

Breaking a long method into smaller methods makes targeted unit testing practical. Learning unit testing reduced client complaints, eliminated false or avoidable bugs, and caught issues earlier. Refactoring separates individual pieces so they can be tested without risking unintended side effects elsewhere. The pattern behind unit testing can be reused by identifying repeated defects, moving detection earlier, creating automated checks, and reducing customer-facing failures. Unit testing is presented as an example of learning a reusable quality pattern rather than merely adopting a tool. Testing should happen after each extraction step instead of only after the full refactor is finished. Client-found bugs in custom systems caused reputational damage because defects reached customers before internal detection.