up-8-deriving-use-case-tests

Derives and maintains the tests of one use case from its specification, in any stack: lists the coverage units (main success scenario, each alternative flow, each business rule with its boundaries, success postconditions, failure guarantees, guarded preconditions, linked testable NFRs), picks the test layer from the use case's interface, writes one traceable test per unit asserting postconditions rather than internals, proves each rule test fails against a deliberately broken rule, and on a specification change updates, deletes or keeps tests according to the difference. Use when the user asks to write, generate, update or review tests for UC-XXX, asks which tests a use case needs, wants spec-based acceptance tests, asks whether the tests really guard a business rule, or suspects generated tests assert the wrong thing. Not for end-to-end journeys across several use cases and not for test-first design of code that has no use case.