Why and How Should You Write Test Code?

Test code goes beyond simply being a tool for finding bugs—it's a core element that boosts development productivity and maintains software quality.

The main reasons to write test code are as follows.

• Reduced debugging costs: Quickly identify the scope of code when problems occur, shortening resolution time.
• Prevention of regression bugs: Prevent existing features from breaking during feature modifications or refactoring, and make them manageable.
• Serving as living documentation: Specify how code behaves, providing more reliable information than separate documentation.
• Improved code quality: Through the process of trying to write code that is easy to test, you naturally end up with well-designed, loosely coupled code.
• Ensuring deployment stability: Through test automation in CI environments, defects are blocked before deployment to production.

For effective testing, it's important to properly organize Unit, Integration, and E2E tests according to the Test Pyramid model.