What is Testability in Laravel, and what role does it play in a real application?

What is Testability in Laravel, and what role does it play in a real application? In Laravel, testability should be understood as part of a larger application architecture rather than as an isolated API call. Many framework facades provide testing support, while constructor injection can make application-specific services even more explicit. A strong understanding includes its purpose, the layer where it belongs, the data or request flow it affects, and the situations where another mechanism may be more appropriate. Practical context: Laravel facades expose convenient interfaces to container-managed services, while helper functions provide common framework utilities. The specific focus here is testability: Many framework facades provide testing support, while constructor injection can make application-specific services even more explicit. 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.