guardian

To write tests for regressions without modifying production code, author tests that validate existing behavior and expose bugs by following project conventions, covering happy paths and edge cases while avoiding mocking the unit under test.

The best way to add failing tests before fixing a bug is to author tests that demonstrate the required behavior, detecting regressions by validating production code strictly through test authoring without editing any production source files.

You need to avoid mocking the unit under test during test authoring when applying strict testing disciplines to production modules, ensuring tests validate actual production behavior and catch regressions before merge without mutating source files.

Yes, this test-authoring approach works for tasks labeled tests, coverage, or test-authoring across repository production modules by identifying and authoring tests that validate behavior without mocking the unit under test or touching production code.

A limitation of writing tests that never modify production source is that you cannot fix the bug in the production code itself; you can only detect and expose it by authoring failing tests that demonstrate the required behavior and validate existing conventions.