skills.rest
maroffo
maroffoCOMMUNITY
Explore all skills by this author →
GitHub

legacy-code-expert

Identify seams and plan characterization tests for legacy code.

16|2|Updated Nov 9, 2025
Search Tags:#testing#refactoring#dependency injection#legacy code#characterization tests#seam identification
One-click install
npx skills add https://github.com/maroffo/claude-forge --skill legacy-code-expert
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: legacy-code-expert
Source: https://github.com/maroffo/claude-forge/tree/main/skills/legacy-code-expert
Command: npx skills add https://github.com/maroffo/claude-forge --skill legacy-code-expert

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill helps developers safely modify legacy code that lacks automated tests, which is a common source of bugs and development slowdowns.

Core Features & Use Cases

  • Dependency Analysis: Identifies and maps dependencies that prevent effective unit testing.
  • Seam Identification: Locates strategic points (seams) in the code where behavior can be altered or observed without modifying the core production logic.
  • Test Planning: Guides the creation of characterization tests to capture existing behavior before changes are made.
  • Transformation Strategy: Recommends specific, low-risk techniques for breaking dependencies and enabling testability.
  • Use Case: You need to add a new feature to a critical, but untestable, 10-year-old Java service. Invoke this skill to understand how to isolate the relevant code section and add tests before making the change.

Quick Start

Use the legacy-code-expert skill to analyze the 'UserAuth.java' file for dependency issues blocking testing.

Frequently Asked Questions about legacy-code-expert

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I safely refactor untested legacy code?▼

To safely refactor untested legacy code, identify seams to alter behavior without modifying production logic, plan characterization tests to capture existing behavior, and break dependencies to enable testability.

What is a seam in legacy code and how does it help with testing?▼

A seam is a strategic point where you can alter or observe behavior without modifying core production logic. Identifying seams allows you to isolate dependencies and introduce characterization tests safely.

How do I break dependencies that block unit testing in legacy applications?▼

Break dependencies blocking unit testing by analyzing code for dependency issues and applying specific transformation strategies for object, preprocessing, and link seams to isolate relevant code sections.

When do I need to write characterization tests for legacy code?▼

You need to write characterization tests before modifying or adding new features to untestable legacy code. This captures existing behavior, ensuring refactoring or dependency breaking does not introduce bugs.

What are the limitations of using dependency injection to refactor legacy code?▼

Dependency injection is one strategy for object seams. Limitations arise when dependencies require preprocessing or link seams instead, necessitating different transformation strategies to break dependencies blocking testability.

Related Skills

Explore More Software Engineering Skills→
abdullah1854abdullah1854
1

codebase-navigation

Map codebase structure, dependencies, and architectural patterns.

Community
Intermediate
venomez-vipervenomez-viper
1

tdd-refactor-guard

Verify test coverage and generate characterization tests before refactoring code.

Community
Advanced
seo-jinseokseo-jinseok

moai-workflow-tdd

Automate the RED-GREEN-REFACTOR cycle for new feature development.

Community
Advanced
Fantasia1999Fantasia1999

tech-debt-tracker

Scans codebases to identify, prioritize, and track technical debt.

Community
Advanced