A methodology that combines verification and conformance testing for validating safety requirements of reactive systems is presented. The requirements are first automatically verifed on the systems specification. Then test cases are automatically derived from the specification and the requirements and executed on a blackbox implementation of the system. The test cases attempt to push the implementation into violating a requirement. We show that an implementation conforms to its specification if and only if it passes all the test cases generated in this way Keywords verification conformance testing safety properties