The Java Engine for Testing (JET) is a system for running distributed automated tests. It has been used by Sun for testing the High Availability DataBase (HADB), JavaDB, PostgreSQL, Memcached, and the MySQL Cluster Manager. JET should be a good way to write your tests if the product you want to test is distributed or has a client/server architecture, if it is natural for you to write the tests in Java, and if you want to invest time in developing tests and abstractions for later reuse.
CODERU is a Java code quality tool to enforce design quality in respect to packages (and therefore modules) dependencies. The Java language is lacking a module concept. CODERU is an approach to close the gap. The approach relies on reserved package names, and the allowed dependency rules between them are expressed in a general way. It includes a Maven plugin for checking your code for rule conformance.