What question did this study set out to answer?

The aim is to modify a legacy business application without tests by using characterization testing to understand its current behavior.

July 29, 2026Open Access

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

GKGo KomuraFujikura (United States)

Key Points

The aim is to modify a legacy business application without tests by using characterization testing to understand its current behavior.
Utilized the golden master method for characterization testing.
Created seams to isolate changes within the application.
Established operational rules to maintain separation between refactoring and feature work.
Outlined a step-by-step procedure for safely modifying the application.
Provided C# examples to illustrate the implementation of the approaches.
Demonstrated how to maintain application stability while adding new features.

Abstract

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.

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

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