Model-based testing using Markov chain usage models provides a powerful way to address testing concerns. Unfortunately, the use of Markov chain usage models on systems which have multiple streams of control, or which have many modeless dialogs, has required approaches which limit automated testing (strong abstractions) or make models difficult to analyze (notations hiding a state explosion). This paper presents a new approach which relies on applying concurrency operators to the test cases generated from simple Markov chain usage models to create sophisticated test cases. This approach leverages existing tools and notations.