This is part of a sequence using TDD to refactor and extend a Stomp client. The earlier posts (not doing much with async code) are
https://6guts.wordpress.com/2016/01/04/not-guts-but-6-part-1... and
https://6guts.wordpress.com/2016/01/05/not-guts-but-6-part-2... . There will be more.