Scala provides an actor library where computation entities, called
actors, communicate by exchanging messages. The schedule of message
exchanges is in general non-deterministic. Testing non-deterministic
programs is hard, because it is necessary to ensure that the system
under test has executed all important schedules. Setac is our proposed
framework for testing Scala actors that (1) allows programmers to
specify constraints on schedules and (2) makes it easy to check test
assertions that require actors to be in a stable state. Setac requires
little change to the program under test and requires no change to the
actor run-time system.  In sum, Setac aims to make it much simpler to
test non-deterministic actor programs in Scala.