Safely Modifying a Legacy Business App That Has No Tests — Characterization Testing and Refactoring in Practice (archived 2026-07-27)

To safely modify a business application with no tests, this article explains, with C# examples, the procedure for a characterization test (the golden master method) that pins down current behavior, how to create seams, and the operational rules for keeping refactoring and feature work separate. Archived version of https://comcomponent.com/en/blog/characterization-test-legacy-refactoring/, as published on 2026-07-27. The live article is maintained and may change after this date. First published 2026-07-17.