Testability

What is the Dependency Inversion Principle?

The Dependency Inversion Principle (the 'D' in SOLID) states that high-level modules should not depend on low-level modules — both should depend on abstraction…

What is the Circular Dependency Anti-Pattern?

A circular dependency is a design flaw where two or more classes (or modules) depend directly on each other, either mutually referencing one another or forming…

Dependency Injection vs Service Locator

Dependency injection has an external party push required collaborators into an object, typically via its constructor, so dependencies appear explicitly in the…

Singleton vs Static Class

A Singleton is a regular class restricted to exactly one instance that is still a real object — it can implement interfaces, be passed around, be subclassed, a…

Active Record vs Repository Pattern

Active Record bundles data and persistence logic (save, find, delete) directly onto the domain object itself, while the Repository pattern separates persistenc…