refactor-test-safety-net

Missing tests are identified by assessing current coverage against the modules you plan to change. Review which unit, integration, snapshot, and regression tests exist for your target code, then prioritize gaps in happy path, error handling, and edge cases before starting refactoring work.

A minimal safety net includes unit tests for isolated functions, integration tests for module interactions, snapshot tests to capture current behavior, and regression tests to verify edge cases. Characterization tests that document actual behavior—not just correctness—are essential for preserving functionality across changes.

Refactoring without pre-existing tests is high-risk. You need a baseline test suite to establish safety before changes. If tests don't exist, create characterization tests first to capture current behavior, then add targeted coverage for the modules you plan to modify.

Run tests after each incremental refactoring step, not just at the end. This catches behavior changes immediately and isolates which modification caused any failure, making debugging faster and keeping your safety net effective throughout the process.

Characterization tests capture what code actually does now, not what it should do ideally. During refactoring, they verify behavior is preserved even if implementation changes. Regular unit tests check correctness; characterization tests baseline current behavior for safe incremental modification.

No—establish a minimal safety net covering happy path, error handling, and known edge cases for targeted modules. Full coverage is ideal but not required to start. Focus tests on the code you plan to change and its immediate dependencies to minimize risk.