Abstract. TTCN-3 is a standardized language for specifying and executing test suites that is particularly popular for testing embedded systems. Prior to testing embedded software in a target environment, the software is usually tested in the host environment. Executing in the host environment often affects the real-time behavior of the software and, consequently, the results of real-time testing. Here we provide a semantics for host-based testing with simulated time and show which kind of timing constraints can be adequately tested with simulated time. We provide a simulated-time solution for distributed testing with TTCN-3. We also report on two case studies where we used simulated time for testing with TTCN-3.