Requirements Coverage
Requirements coverage denotes the degree to which requirements are covered by other development artifacts — typically by test cases. A requirement counts as “covered” if it is linked directly or indirectly via trace links to at least one artifact of the target type. Measuring it therefore requires requirements traceability.
How coverage can be meaningfully defined and analyzed in practice is described in our article What Is Requirements Coverage and How Can It Be Analyzed?
Why is the term ambiguous?
Requirements coverage is not uniformly defined: most available definitions are tied to commercial requirements management tools and are limited to the direct relationship between requirement and test case. At the same time, process standards such as Automotive SPICE require that the selection of test cases ensures sufficient coverage — especially in safety-critical development. In practice, the coverage definition therefore has to be adapted to one’s own development process.
Direct vs. transitive coverage
In a development process following the V-model, the direct relationship between requirement and test case is not sufficient:
- Direct coverage: a requirement is linked to at least one test case on the same level.
- Transitive (deep) coverage: a requirement only counts as covered once all requirements derived from it on lower levels — recursively — are covered as well. A customer requirement is thus only “covered by tests” once the entire derivation chain down to the low-level tests is closed.
This allows graduated progress statements — for example: a customer requirement is analyzed (covered by high-level requirements), implemented (deeply covered by low-level requirements) or covered (deeply covered by test cases).
Coverage analysis in practice
The common entry-level approach is a traceability matrix — but with several V-model levels and thousands of artifacts, it quickly becomes unmaintainable. Scalable coverage analyses require a dedicated traceability tool with dynamic queries across the artifact graph. Read more on our page Requirements Traceability.