MRUnit使用实例

下面简单介绍MRUnit的使用方法

1、下载
http://archive.apache.org/dist/mrunit/mrunit-1.0.0/
本人下载：apache-mrunit-1.0.0-hadoop2-bin.tar.gz
2、安装
tar -axvf apache-mrunit-1.0.0-hadoop2-bin.tar.gz -C 指定的路径
将lib下除了commons-logging-1.1.1.jar，其余的jar都导入到测试工程中
3、测试
本例使用简化的MaxTemperature实例

Map类：
	public class MaxTemperatureMapper extends Mapper {
	private static final int MISSING = 9999;

	public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
		String line = value.toString();
		String year = line.substring(0, 4);
		int airTemperature;
        airTemperature = Integer.parseInt(line.substring(5, 7));
		String quality = line.substring(8, 11);
		if (airTemperature != MISSING && quality.equals("123"))
		context.write(new Text(year), new IntWritable(airTemperature));
	    }
    }
	
	Reduce类：
	public class MaxTemperatureReducer extends Reducer {

	public void reduce(Text key, Iterable values, Context context)
			throws IOException, InterruptedException {

		int maxValue = Integer.MIN_VALUE;
		for (IntWritable val : values)
			maxValue = Math.max(maxValue, val.get());

		context.write(key, new IntWritable(maxValue));
		}
	}
	
	Map测试类：
	public class MaxTemperatureMapperTest {
	@Test
	public void processesValidRecord() throws IOException, InterruptedException {
		Text value = new Text("1950-30-123");   //模拟的输入数据
		int result = 30;
		new MapDriver()
				.withMapper(new MaxTemperatureMapper())    //map类
				.withInput(new LongWritable(0), value)     //输入Text
				.withOutput(new Text("1950"), new IntWritable(result))  //预期的输出结果
				.runTest(); //运行测试
		}
	}
	
	Reduce测试类：
	
	public class MaxTemperatureReducerTest {  
    @Test  
    public void returnsMaximumIntegerInValues() throws IOException, InterruptedException {  
        new ReduceDriver()  
            .withReducer(new MaxTemperatureReducer())     //Reduce类
            .withInput(new Text("1950"), Arrays.asList(new IntWritable(10), new IntWritable(5)))  //模拟的Reduce输入
            .withOutput(new Text("1950"), new IntWritable(10))   //预期的输出结果
            .runTest();  //运行测试
		}  
	}  
	

以jUnit test 方式运行测试类即可