How to write unit tests for your Hadoop MapRecude jobs

Simple answer: use MRUnit.

You will need a classifier to include it in your maven project:

  <dependency>
   <groupId>org.apache.mrunit</groupId>
   <artifactId>mrunit</artifactId>
   <version>1.0.0</version>
   <classifier>hadoop2</classifier>
   <scope>test</scope>
  </dependency>