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testing-patterns

Document and apply testing patterns for safe refactoring in TypeScript and JavaScript codebases.

Updated Jan 14, 2026
One-click install
npx skills add https://github.com/primeinc/swarm --skill testing-patterns-primeinc
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: testing-patterns
Source: https://github.com/primeinc/swarm/tree/main/packages/opencode-swarm-plugin/global-skills/testing-patterns
Command: npx skills add https://github.com/primeinc/swarm --skill testing-patterns-primeinc

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill helps engineers document and apply proven testing patterns to improve code testability and safety when refactoring or characterizing unfamiliar code.

Core Features & Use Cases

  • Characterization Tests: Document actual code behavior to guide safe changes.
  • Seam and Dependency-Breaking Techniques: Identify points of variability and introduce safe tests around legacy code.
  • Safe Refactoring Guidance: Provides patterns like Sprout Methods, Extract Interface, and Push Down Dependency to reduce risk during change.
  • Use Case: When taking over a legacy module, characterize its behavior with tests before making changes and gradually replace hard dependencies with test doubles.

Quick Start

Start by reading the dependency-breaking catalog and outline which patterns fit your codebase, then add a characterization test to a small module to observe actual behavior.

Frequently Asked Questions about testing-patterns

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

FAQPage Schema
How do I write characterization tests for legacy TypeScript and JavaScript modules?▼

Characterization tests document actual code behavior before refactoring legacy modules. You write tests capturing current outputs to establish a safety baseline, enabling safer changes in complex TypeScript and JavaScript codebases.

What is a seam in legacy code and how do I use it for safe dependency breaking?▼

A seam identifies points of variability in legacy code where you can alter behavior without editing that exact location. Using seams enables safe dependency-breaking techniques to introduce test doubles and isolate modules for testing.

How do I refactor unsafe legacy code with hard dependencies using sprout methods?▼

Sprout Methods allow you to add new logic in a separate method rather than modifying risky legacy code. This testing pattern reduces change risk by isolating new functionality alongside existing hard dependencies.

When should I use characterization tests instead of standard unit tests?▼

Use characterization tests when taking over unfamiliar legacy codebases where actual behavior is unknown. Unlike standard unit tests defining desired behavior, they capture existing behavior to guide safe refactoring and prevent regressions.

What's the best way to start introducing test doubles into a complex JavaScript codebase?▼

Start by reading the dependency-breaking catalog to outline fitting patterns, then add a characterization test to a small module. Gradually replace hard dependencies with test doubles using Extract Interface and Push Down Dependency patterns.

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