Marcin Grzejszczak is an experienced Java programmer, and an enthusiast of clean coding and good design. He is also fond of JVM-based languages such as Groovy and Scala. Marcin is interested in the concept of unit testing and rule engines. That is why he wrote this book about Mockito library and became a contributor to the JBoss Drools project. He digs into the aforementioned languages and technologies on his blog at http://toomuchcoding.blogspot.com.