80f59fd3b3
- Extract pure game logic functions to game-logic.js for testability - Add Jest testing framework with 57 tests covering: * Unit tests for pure functions (createEmptyBoard, checkBoardOverflow, etc.) * Integration tests for garbage system (addGarbageToPlayer, sendGarbage) * Socket.io integration tests for multiplayer flow - Refactor index.js to use extracted functions - Tests verify garbage elimination bug fix: players only eliminated when board overflows