UCTSystem is a prototype tool designed to perform automatic test generation from UML requirements. It uses UML use cases enhenced with contracts (i.e. precondition and postconditions) to build an execution model allowing all valid sequences of use cases. Using this execution model and several test criteria, it generates test objectives as sequence of use cases to exerce. It includes both criteria for functional testing and a criterion for robusness testing. Those test objectives are then mapped into test cases using test templates.