We propose an approach to test object-based specifications using B notations. We start from an UML specification in the form of a class diagram and sequence diagrams which express scenarios modelling the system's behavior. These diagrams are transformed into a B specification which is completed by the definition of the operations (messages in the sequence diagrams corresponding to the methods in the class diagram), and safety and dynamic properties on the system. The test of scenarios and the satisfaction of the properties is done by means of a theorem prover.