Saga basic concept and unit test reference list

In DDD/CQRS, A saga is a “long-lived business transaction or process between aggregates”, also call process manager

http://blog.jonathanoliver.com/cqrs-sagas-with-event-sourcing-part-i-of-ii/
http://blog.jonathanoliver.com/cqrs-sagas-with-event-sourcing-part-ii-of-ii/
How to unit test saga
http://www.udidahan.com/2008/02/04/sagas-and-unit-testing-business-process-verification-made-easy/
http://docs.particular.net/nservicebus/sagas/