Googlielmo's blog

Apache MRUnit ( https://mrunit.apache.org/ ) is an Open Source library that allows unit-testing for Hadoop Mappers, Reducers, and MapReduce programs. It provides a convenient integration between MapReduce and standard testing libraries such as JUnit and Mockito and helps (providing a set of interfaces and test harnesses) bridging the gap between MapReduce programs and those traditional libraries. It doesn't replace JUnit, but works on top of it. Before reading further, please be aware that knowledge of Hadoop MapReduce and JUnit is required for a better understanding of this post. The three core classes of MRUnit are the following: • MapDriver : the driver class responsible for calling the Mapper’s map() method. • ReducerDriver : the driver class responsible for calling the Reducer’s reduce() method. • MapReduceDriver : the combined MapReduce driver responsible for calling the Mapper’s map() method first, followed by an in-memory Shuffle phase. At the end of this phase the ...