Unit tests should follow the FIRST rules (Fast, Isolated, Repeatable, Self-Validated and Timely). When persistence layer is under test, fast and isolated rules are the most violated. For relational database management systems, embedded databases and DbUnit framework exist to help us to not break them, but there is no like DBUnit framework for heterogeneous NoSQL systems.
NoSQLUnit aids us to not break these rules by providing a JUnit extension which helps us to manage lifecycle of NoSQL systems and also it takes care of maintaining databases into known state. NoSQLUnit can be used during unit tests, but also in high level tests like integration or acceptance tests.
Video source: http://www.parleys.com/play/5148922b0364bc17fc56c95f/chapter0/about
Video producer: http://www.devoxx.com/
Further reading: NoSQLUnit – Unit Testing for Java NoSQL Applications