In this paper, we demonstrate a method that uses the model transformation technology of MDA to generate unit test cases from a platform-independent model of the system. The method we propose is based on sequence diagrams. First we model the sequence diagram and then this model is automatically transformed into a general unit test case model (an xUnit model which is independent of a particular unit testing framework), using model-to-model transformations. Then model-to-text transformations are applied on the xUnit model to generate platformspecific (JUnit, SUnit etc.) test cases that are concrete and executable. We have implemented the transformations in a prototype tool based on the Tefkat transformation tool and MOFScript. The paper gives details of the tool and the transformations that we have developed. We have applied the method to a small example (ATM Simulation).