In this recipe, we are going to learn how to unit test the map reduce code using a library called MRUnit.
To perform this recipe, you should have a running Hadoop cluster as well as an eclipse similar to an IDE.
Sometimes, it is very difficult to develop, compile, deploy and execute the map reduce program and then figure out whether the code is correct or not. In order to avoid this deploying and testing technique, we can use a unit testing framework that's been built specially for Map Reduce called, MRUnit.
Let's assume that we have a map reduce program that emits and counts words starting with '#', such as a Twitter hashtag counter. The Mapper code for this hashtag counter looks like this:
public static class TokenizerMapper extends
Mapper<Object, Text, Text, IntWritable> {
private static final IntWritable one = new IntWritable(1);
private Text word = new Text();
public void...