title: What is the relationship between requirements and test cases?
body: <p>I see that there are many systems out there for requirements to test cases traceability and I started to ask myself what the relationship is between these two artefacts.  For example, why have the notion of test cases as opposed to just calling them detailed requirements?  Are test cases in fact a refinement of the requirements set?  If test cases are not requirements and require more than the documented requirements (e.g. testing more errors, etc) then surely the requirements set is incomplete?  Are requirements just abstract test cases?</p>