MRUNIT hadoop逐步调试工具！

MRUNIT hadoop MapReduce逐步调试工具！

MRUnit简介
MRUnit是一款由Couldera公司开发的专门针对Hadoop中编写MapReduce单元测试的框架。可以用MapDriver单独测试
Map，用ReduceDriver单独测试Reduce，用MapReduceDriver测试MapReduce作业。
实战
我们将利用MRUnit对本系列上篇文章MapReduce基本编程中的字数统计功能进行单元测试。
加入MRUnit依赖<dependency>
<groupId>com.cloudera.hadoop</groupId>
<artifactId>hadoop-mrunit</artifactId>
<version>0.20.2-320</version>
<scope>test</scope>
</dependency>
单独测试Map
public class WordCountMapperTest {
private Mapper mapper;
private MapDriver driver;
@Before
public void init(){
mapper = new WordCountMapper();
driver = new MapDriver(mapper);
}
@Test
public void test() throws IOException{
String line = "Taobao is a great website";
driver.withInput(null,new Text(line))
.withOutput(new Text("Taobao"),new IntWritable(1))
.withOutput(new Text("is"), new IntWritable(1))
.withOutput(new Text("a"), new IntWritable(1))
.withOutput(new Text("great"), new IntWritable(1))
.withOutput(new Text("website"), new IntWritable(1))
.runTest();
}
}
上面的例子通过MapDriver的withInput和withOutput组织map函数的输入键值和期待的输出键值，通过runTest方法运行
作业，测试Map函数。测试运行通过。
单独测试Reduce
public class WordCountReducerTest {
private Reducer reducer;
private ReduceDriver driver;
@Before
public void init(){
reducer = new WordCountReducer();
driver = new ReduceDriver(reducer);
}
@Test
public void test() throws IOException{
String key = "taobao";
List values = new ArrayList();

values.add(new IntWritable(2));
values.add(new IntWritable(3));
driver.withInput(new Text("taobao"), values)
.withOutput(new Text("taobao"), new IntWritable(5))
.runTest();
}
}
上面的例子的测试Map函数的写法类似，测试reduce函数，
因为reduce函数实现相加功能，因此我们假设输入为<taobao,[2,3]>，
则期待结果应该为<taobao,5>.测试运行通过。
测试MapReduce
public class WordCountTest {
private Mapper mapper;
private Reducer reducer;
private MapReduceDriver driver;
@Before
public void init(){
mapper = new WordCountMapper();
reducer = new WordCountReducer();
driver = new MapReduceDriver(mapper,reducer);
}
@Test
public void test() throws RuntimeException, IOException{
String line = "Taobao is a great website, is it not?";
driver.withInput("",new Text(line))
.withOutput(new Text("Taobao"),new IntWritable(1))
.withOutput(new Text("a"),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))
.withOutput(new Text("website"),new IntWritable(1))
.runTest();
}
}
这次我们测试MapReduce的作业，通过MapReduceDriver的withInput构造map函数的输入键值，通过withOutput构造
reduce函数的输出键值。来测试这个字数统计功能，这次运行测试时抛出了异常，测试没有通过但没有详细junit异常信
息，在控制台显示