Software testing is considered as a dominant factor for producing high quality software systems. Testing is a costly activity and constitutes more than fifty percent of software development cost. In this paper, we propose a method to generate a suite of test cases using model-based testing technique that takes as an input a model of a system specified in Constraints-based Modular Petri-nets (CMPNs) and scenarios. More specifically, scenarios are used to document system requirements and are transformed into Constraints-based Modular Petri-nets (CMPNs). Using the CMPNs as a model for model-based testing purpose, we then should be able to automatically generate system level test cases. The feasibility of this work is illustrated by a simple case study.