With the increasing use of computer systems for controlling processes and activities in our everyday surroundings, the correctness of these systems becomes increasingly important. The functionality of such control systems often relies on tasks being performed at the correct time, not to soon and not to late. In this report we investigate the contemporary practices for ensuring correct behaviour of such real-time systems. We identify the quality and applicability measures of current practices as well as their limitations. Based on the contemporary methods, we propose a method for validating embedded real-time systems The proposed method allows real-time systems to be validated in simulated environments. The simulation performed is based on formal descriptions (models) of the environments. During simulation, the structure of the model is used by a guiding algorithm to achieve an interesting exploration of the possible behaviour. Furthermore, validation is performed in terms of the states of the environment. A prototype of the proposed method has been implemented. Based on this prototype we carry out a case study illustrating the process of describing and formalising the environment as well as validating programs controlling it.