# Tdd Legacy Rescue > Strategies for bringing legacy code under test and refactoring it safely. Use when this capability is needed. - Skill: `tomevault-io/tdd-legacy-rescue` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/tdd-legacy-rescue` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/tdd-legacy-rescue/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/tdd-legacy-rescue --- # Legacy Code Rescue "Legacy code is code without tests." — Michael Feathers ## Rescue Strategies ### 1. Sprout Method / Class - When you need to add functionality, write it as new, tested code (a "sprout") and call it from the legacy code. - **Benefit**: Ensures new code is tested immediately. ### 2. Wrap Method / Class - Wrap an existing method or class with a new one that contains the new logic and calls the original. - **Benefit**: Provides a clear boundary for testing new behavior. ### 3. Breaking Dependencies - Identify "Seams" (places where you can change behavior without editing code in that place). - Use Dependency Injection or Subclass & Override to isolate the logic you want to test. ## The Rescue Cycle 1. Identify a target for change. 2. Find a Seam and break dependencies. 3. Write a characterization test (to document current behavior). 4. Apply your change using TDD. 5. Refactor with the safety of your new tests. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/jcorpac) — claim your Tome and manage your conversions.