Model-based conformance testing of reactive systems consists in taking benefit from the model for mechanizing both test data generation and verdicts computation. On-line test case generation allows one to apply adaptive on-the-fly analyzes to generate the next inputs to be sent and to decide if observed outputs meet intended behaviors. On the other hand, in off-line approaches, test suites are pre-computed from the model and stored under a format that can be later performed on test-beds. In this paper, we propose a two-passes off-line approach where: for the submission part, a test suite is a simple timed sequence of numerical input data and waiting delays, and then, the timed sequence of output data is post-processed on the model to deliver a verdict. As our models are Timed Output Input Symbolic Transition Systems, our off-line algorithms involve symbolic execution and constraint solving techniques.