refactor-without-breaking-behavior

To refactor legacy code without breaking existing behavior, identify safe seams, write characterization tests, and apply incremental changes validated by regression coverage. This approach prevents small edits from rippling into unintended side effects.

A safe seam is a specific location in legacy code where you can safely perform extraction, renames, or deduplication without altering external behavior. Identifying these seams allows you to isolate risky changes and stage edits incrementally.

Yes, you need characterization tests before refactoring risky legacy code to establish regression coverage. These tests capture the current behavior, allowing you to verify that your incremental changes preserve the original functionality.

The best way to execute module extraction is to select a safe seam, add regression coverage, and perform small incremental commits. This behavior-preserving refactor method ensures structural changes are isolated and validated against tests.

Yes, this approach works for codebase cleanup and simplification by staging edits incrementally with regression coverage. It is designed to handle structural changes like deduplication while keeping behavior constant across versions.

You should avoid behavior-preserving refactors when you lack the ability to establish characterization tests or regression coverage. Without tests to validate outcomes, incremental changes risk introducing unintended behavior modifications.