0、preliminary 环境搭建

Setup development environment

Download the latest version of MRUnit jar from Apache website: https://repository.apache.org/content/repositories/releases/org/apache/mrunit/mrunit/. For example if you are using the Hadoop version 1.0.3, download mrunit-x.x.x-incubating-hadoop2.jar.
Include the jar in your IDE classpath. Also download the latest verison of mokito (http://code.google.com/p/mockito/) and JUnit jar and add them to your class path of development environment.
请导入jar包到CentOS中的eclipse

download site: https://mrunit.apache.org/general/downloads.html

download web site https://repository.apache.org/content/repositories/releases/org/apache/mrunit/mrunit/1.1.0/

You should Attention:

hadoop 框架包里面有自带的mock jar包，吧他们全部删除，否则要产生jar包兼容性异常（编译器不晓得调哪个jar包为好）

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转自： http://www.infoq.com/cn/articles/HadoopMRUnit

(请关心里面的干货——测试用例文末)

引言

Hadoop MapReduce作业有着独一无二的代码架构，这种代码架构拥有特定的模板和结构。这样的架构会给测试驱动开发和单元测试带来一些麻烦。这篇文章是运用MRUnit，Mockito和PowerMock的真实范例。

我会介绍

使用MRUnit来编写Hadoop MapReduce应用程序的JUnit测试
使用PowerMock和Mockito模拟静态方法
模拟其他类型中的业务逻辑（译注：也就是编写测试驱动模块）
查看模拟的业务逻辑是否被调用（译注：测试驱动模块是否运行正常）
计数器
测试用例与log4j的集成
异常处理

本文的前提是读者应该已经熟悉JUnit 4的使用。

使用MRUnit可以把测试桩输入到mapper和/或reducer中，然后在JUnit环境中判断是否通过测试。这个过程和任何JUnit测试一样，你可以调试你的代码。MRUnit中的MapReduce Driver可以测试一组Map/Reduce或者Combiner。 PipelineMapReduceDriver可以测试Map/Reduce作业工作流。目前，MRUnit还没有Partitioner对应的驱动。MRUnit使开发人员在面对Hadoop特殊的架构的时候也能进行TDD和轻量级的单元测试。

测试用例（MapTest + ReduceTest + MapReduceTest）

publicclass MapTest {

private Mapper mapper;
private MapDriver driver;@Before
publicvoid init(){mapper = new WordCount.Map();driver = new MapDriver(mapper);
}@Test
publicvoid test() throws IOException{String line = "this is a test case for map";driver.withInput(new LongWritable(1),new Text(line)).withOutput(new Text("this"), new IntWritable(1)).withOutput(new Text("is"), new IntWritable(1)).withOutput(new Text("a"), new IntWritable(1)).withOutput(new Text("test"), new IntWritable(1)).withOutput(new Text("case"), new IntWritable(1)).withOutput(new Text("for"), new IntWritable(1)).withOutput(new Text("map"), new IntWritable(1)).runTest();
}

}

publicclass ReduceTest {

private Reducer reducer;
private ReduceDriver driver;@Before
publicvoid init(){reducer = new WordCount.Reduce();driver = new ReduceDriver(reducer);}
@Test
publicvoid test() throws IOException{String key = "test";List<IntWritable> values = new ArrayList();values.add(new IntWritable(2));values.add(new IntWritable(3));//5        driver.withInput(new Text(key),values).withOutput(new Text("test"), new IntWritable(5)).runTest();
}

}

publicclass MapReduceTest {

private Reducer reducer;
private Mapper mapper;    
private MapReduceDriver driver;@Before
publicvoid init(){reducer = new WordCount.Reduce();mapper = new WordCount.Map();driver = new MapReduceDriver(mapper,reducer);
}
@Test
publicvoid test() throws IOException{String line = "chinacache is a great CDN is it not";driver.withInput(new LongWritable(1),new Text(line)).withOutput(new Text("CDN"), new IntWritable(1)).withOutput(new Text("a"), new IntWritable(1)).withOutput(new Text("chinacache"), new IntWritable(1)).withOutput(new Text("great"), new IntWritable(1)).withOutput(new Text("is"), new IntWritable(2)).withOutput(new Text("it"), new IntWritable(1)).withOutput(new Text("not"), new IntWritable(1)).runTest();
}

}