Why is Unit tests important in Laravel applications, and what problem does it solve for developers?

Why is Unit tests important in Laravel applications, and what problem does it solve for developers? The key reason to understand unit tests is that Laravel applications are usually composed of several layers that must work together predictably. Unit tests focus on isolated classes or functions with limited framework and database interaction. Ignoring that boundary can lead to duplicated logic, poor security, unnecessary database work, or code that is difficult to test. Why it matters in practice: Laravel provides testing support for unit and feature tests so teams can verify business rules and application behavior automatically. The specific focus here is unit tests: Unit tests focus on isolated classes or functions with limited framework and database interaction. This question is designed to test not only terminology, but also how the concept fits into Laravel's request, application, database, security, or deployment workflow.