tdd-refactor-guard

Test coverage validation before refactoring involves scanning target code for existing tests, assessing public method coverage, and generating missing characterization tests to lock in current behavior. This prevents accidental functional changes by validating observable behavior prior to modifications.

Characterization tests are tests created to lock in the current behavior of existing code before refactoring begins. You need them when restructuring methods or extracting logic without sufficient test coverage, ensuring the refactored output preserves the original observable behavior.

To check test quality before an AI-assisted framework migration, validate that tests verify observable behavior rather than implementation details. Flagging low-value tests ensures your suite will actually catch regressions instead of passing trivial assertions during the migration.

Yes, this refactoring approach works for legacy modules by first identifying the target code scope, assessing existing test coverage, and generating missing tests to cover public methods and edge cases before any restructuring or method extraction begins.

Refactoring breaks functionality when existing tests pass because low-value tests verify implementation details rather than observable behavior. Validating test quality and adding characterization tests prevents undetected regressions by ensuring tests actually catch functional changes.