Regression Tester

Overview

This skill creates a safety net around refactoring work. It analyzes what changed, identifies the public API surface and behavior contracts of the refactored code, generates targeted regression tests that verify behavior is preserved, and runs them against both the old and new implementations to confirm equivalence.

Instructions

Step 1: Analyze the Refactoring Scope

1. Get the diff: git diff main...HEAD or compare specific commits

2. Categorize changes:

   • Signature changes — function/method names, parameters, return types
   • Internal restructuring — same API, different implementation
   • Extracted modules — code moved to new files/functions
   • Behavioral changes — intentional behavior modifications (flag these!)

3. Identify the behavior contract for each changed unit:

   • What inputs does it accept?