We introduce a prototype testing framework as an extension of JUnit for testing actor-based systems. Our framework runs a given JUnit test in various schedules and records the execution trace for each run. In case a failure is observed during one of the test runs, the corresponding execution trace is compared with those traces associated with passed test runs. The sequence of exchanged messages that are different with respect to these runs are extracted. A UML sequence diagram is automatically generated to depict this sequence. Hence, the developer can observe the interleaving of messages that caused the failure. We illustrated the application of our framework on two sample actor-based software systems.