There is a common misconception about mandatory interfaces for easy unit testing and mocking. This myth causes a lot of plumbing in Java EE projects. This screencast shows how to mock classes directly--without any interfaces:
NEW workshop: Building HTML 5 Applications Without Frameworks, Full week in December 2016: from Java EE 7 Bootstrap, Effective, Architectures over Testing to Microservices
On demand workshops: Java EE 7: Bootstrap, Effective, Testing and Microservices available for streaming.