What problem does it solve? Code that relies on static methods, global state, hidden dependencies, and mixed concerns is difficult to unit test and maintain. This Skill provides a concrete rulebook for writing Java/Spring classes that are small, focused, and independently testable. ## Core Features & Use Cases - LEGO Bricks Design Rules: Enforces single-responsibility classes (≤200 LOC) and methods (≤30 LOC) with self-explanatory names and clear input/output contracts. - SOLID-to-Testability Mapping: Shows how SRP, OCP, LSP, ISP, and DIP each translate into concrete testability benefits with Java code examples. - Anti-Pattern Detection: Identifies static business logic, global state, hidden dependencies, and mixed concerns, with refactored alternatives. - Use Case: Before writing a new Spring service, apply the checklist to inject dependencies via constructor, avoid statics, and keep each class focused on one responsibility so unit tests can mock collaborators easily. ## Quick Start Ask the AI to review the current Java class against the testable-code-principles checklist and refactor any static methods, hidden dependencies, or mixed concerns it finds.
