The Safe Way to Test Untested Code

Adding tests to untested production code is deceptively dangerous—developers often misunderstand the actual behavior, leading to test suites that pass but production failures. This workflow demonstrates how to use Claude Code with characterization tests to capture real behavior before refactoring, creating a safety net for critical legacy code. It's an essential strategy for teams managing undocumented code that's too risky to modify without proving what it actually does first.