characterization-testing

Characterization tests capture the current behavior of legacy code before refactoring by generating behavioral snapshots. This creates a safety net that ensures refactoring efforts do not introduce regressions or unintentionally change pre-refactoring states.

Generating golden tests for ViewModels, Repositories, Services, and Widgets uses ApprovalTests for deterministic snapshotting. This approach documents the exact current outputs of these components, locking them into verified states before any code modifications begin.

ApprovalTests document undocumented code behavior by snapshotting the outputs of existing execution paths. This method captures the actual current state of complex modules, such as authentication flows, without requiring prior knowledge of the intended design.

Yes, you can generate characterization tests for Widget components alongside ViewModels, Repositories, and Services. The automated test generation captures the deterministic rendering and interaction behaviors of these UI elements before you begin refactoring.

You need characterization tests instead of standard unit tests when refactoring legacy code with undocumented behavior. They focus on capturing what the code currently does rather than what it should do, providing a safety net for complex modules where expected behavior is unknown.

Characterization testing works for complex authentication modules by generating tests that document current sign-in, sign-up, and error handling behaviors. This captures the existing authentication logic precisely, ensuring refactoring efforts preserve pre-refactoring states without introducing regressions.