Temporal correctness is crucial for real-time systems. There are few methods to test temporal correctness and most methods used in practice are ad-hoc. A problem with testing real-time applications is the response-time dependency on the execution order of concurrent tasks. Execution orders in turn depends on scheduling protocols, task execution times, and use of mutual exclusive resources apart from the points in time when stimuli is injected. Model-based mutation testing has previously been proposed to determine the execution orders that need to be tested to increase confidence in timeliness. An effective way to automatically generate such test cases for dynamic real-time systems is still needed. This paper presents a method using heuristic-driven simulation for generation of test cases.