This is the second article that describes how to test asynchronous operations with the Byteman framework in an application using the Spring framework. The article discuss how to implement the Spock framework, while the first, "Testing Asynchronous Operations in Spring With JUnit and Byteman", focuses on implementing tests with JUnit4.
It's not necessary to read the previous article because all of the essentials are going to be repeated. Nevertheless, I encourage you to read that article if you are interested in testing asynchronous operations with JUnit.