Testing is a cornerstone of modern application development. As applications grow in size and complexity, manual verification becomes insufficient, error-prone, and slow. Automated testing provides a systematic way to ensure correctness, maintain quality, and evolve systems with confidence. In the world of ASP.NET Core, testing is not an afterthought but a built-in part of the framework’s philosophy. Dependency Injection, configuration patterns, and modular design all contribute to making ASP.NET Core applications inherently testable.