hadoop中使用Mockito进行单元测试

由于hadoop中mapper和reducer这两个组件相互依赖，对这种测试传统的Junit单元测试可能不满足我们的需求。我们可以使用Mockito代替hadoop组件来对hadoop的mapper和reducer函数进行测试。下面我展示以计算ncdc中最高气温的map函数进行单元测试。

1、导入Mockito的jar包，一般hadoop工程中自带这个jar，如果没有自己去网上下载，这里不多说；

 

2、编写Mapper行数，这里的Mapper函数等下用来Mockito来单元测试，MaxTemperatureMapper类如下：该类实现了从ncdc气象数据中读取数据，并以年份为key,气温为value

package org.wucl.hadoop.maxtemperature;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class MaxTemperatureMapper extends
		Mapper<LongWritable, Text, Text, IntWritable> {

	private static final int MISSING = 9999;

	@Override
	protected void map(LongWritable key, Text value, Context context)
			throws IOException, InterruptedException {
		String line = value.toString();
		String id = line.substring(15, 19);
		int airTemperature;
		if (line.charAt(87) == '+') {
			airTemperature = Integer.parseInt(line.substring(88, 92));
		} else {
			airTemperature = Integer.parseInt(line.substring(87, 92));
		}
		String quality = line.substring(92, 93);
		if (airTemperature != MISSING && quality.matches("[01459]")) {
			context.write(new Text(id), new IntWritable(airTemperature));
			//System.out.println(airTemperature);
		}
	}

}

（不熟悉ncdc 气象数据结构的tx自己百度或google，自己动手，丰衣足食）

3、构建Context实例：为对上面的map函数就行单元测试，首先需要构件一个Context实例，可以使用Mockito的mock方法来构建：

代码如下：

Context context = mock(Context.class);

（当然，类前需要静态导入Mockito包这里才可以肆无忌惮的直接调用mock()方法，后面将贴出完整代码）

 

4、调用map函数：context实例创建完成后就可以创建Mapper对象并调用map方法了：

		MaxTemperatureMapper mapper = new MaxTemperatureMapper();
		Text value = new Text(
				"0043011990999991950051518004+68750+023550FM-12+0382" +
				        // Year ^^^^
						"99999V0203201N00261220001CN9999999N9-00111+99999999999");
		                                                      // Temperature ^^^^^
		mapper.map(null, value, context);

5、断言：和junit的Assert有点像，还是直接看代码明白的快：

verify(context).write(new Text("1950"), new IntWritable(-11));

运行结果如下：

下面贴出Mockito完整的代码：

package org.wucl.hadoop.maxtemperature;

import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.junit.Test;

public class MaxTemperatureMapperTest {

	@Test
	public void processesValidRecord() throws IOException, InterruptedException {
		Context context = mock(Context.class);
		MaxTemperatureMapper mapper = new MaxTemperatureMapper();
		Text value = new Text(
				"0043011990999991950051518004+68750+023550FM-12+0382" +
				        // Year ^^^^
						"99999V0203201N00261220001CN9999999N9-00111+99999999999");
		                                                      // Temperature ^^^^^
		mapper.map(null, value, context);
		verify(context).write(new Text("1950"), new IntWritable(-11));
	}

	@Test
	public void processesValidRecord2() throws IOException,
			InterruptedException {
		Context context = mock(Context.class);
		MaxTemperatureMapper mapper = new MaxTemperatureMapper();
		Text value = new Text(
				"0043011990999991950051518004+68750+023550FM-12+0382" +
				        // Year ^^^^
						"99999V0203201N00261220001CN9999999N9+00201+99999999999");
		                                                      // Temperature ^^^^^
		mapper.map(null, value, context);
		verify(context).write(new Text("1950"), new IntWritable(20));
	}

}