public void Tell_TracedMessage_TracerAroundReceiveCalled() { //setup IAkkaTracer tracer = Substitute.For <IAkkaTracer>(); IScope scope = Substitute.For <IScope>(); tracer.AroundReceive(null, null, null).ReturnsForAnyArgs(scope); var tep = new TracingExtensionProvider(new SubsTracingExtensionFactory(tracer)); Sys.RegisterExtension(tep); var testActor = new TestActorRef <SampleActor>(Sys, Props.Create(() => new SampleActor())); //sync actor //call testActor.Tell(new TracedMessage("exception", null)); //assert tracer.ReceivedWithAnyArgs(1).AroundReceive(null, null, null); }