在单元测试中使用EasyMock

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我们每天的开发中都要编写大量的单元测试，很多单元测试的对象是相对独立的，例如一个所得税计算的模块，但是更多的单元测试需要依赖其他的组件或者服务。因此，我们需要EasyMock来无缝的连接这些组件。Mock的意思就是空的，不存在的东西。

EasyMock刚刚发布了2.2版本，它开始使用很多基于jdk 1.5的特性。

下面我们举一个例子：

假设定义一个如下的接口：

public interface ISimpsonService {
IEpisode getEpisode(int number);
}

public interface IEpisode {
    int getNumber();
   String getTitle();
   InputStream getDataAsStream();
}

该接口的实现为

public class ClientSimpsonService implements ISimpsonService {    private ISimpsonService remoteSimpsonService;    public ClientSimpsonService(ISimpsonService remoteSimpsonService) {        this.remoteSimpsonService = remoteSimpsonService;    }    public IEpisode getEpisode(int episodeNumber) {        return null;    }}

对该服务的单元测试如下

public class ClientSimpsonServiceTest extends TestCase {    public void testClientSimpsonService() {        try {            new ClientSimpsonService(null);            fail("Expected IllegalArgumentException");        } catch (IllegalArgumentException e) {            // expected        }    }

我们可以看到因为没有remoteSimpsonService，所以我们只传一个null给ClientSimpsonService，

这样是无法完成测试的。所以我们把还没有写的remoteSimpsonService用mock替代。

import static org.easymock.EasyMock.createMock;import junit.framework.TestCase;public class ClientSimpsonServiceTest extends TestCase {    private ISimpsonService remoteSimpsonServiceMock;    protected void setUp() throws Exception {        super.setUp();        remoteSimpsonServiceMock =            createMock(ISimpsonService.class);    }    public void testClientSimpsonService() {        try {            new ClientSimpsonService(null);            fail("Expected IllegalArgumentException");        } catch (IllegalArgumentException e) {            // expected        }        new ClientSimpsonService(remoteSimpsonServiceMock);    }}

上面的黑体代码中，我们创建了一个ISimpsonService.class的mock，它拥有和ISimpsonService一样的

接口。

同样的方法，我们可以定义ISimpsonService返回的对象IEpisode

import static org.easymock.EasyMock.createMock;import static org.easymock.EasyMock.expect;import static org.easymock.EasyMock.replay;import static org.easymock.EasyMock.verify;import junit.framework.TestCase;public class ClientSimpsonServiceTest extends TestCase {    private IEpisode episode17Mock;    private ISimpsonService remoteSimpsonServiceMock;    protected void setUp() throws Exception {        super.setUp();        episode17Mock = createMock(IEpisode.class);        remoteSimpsonServiceMock =            createMock(ISimpsonService.class);    }...    public void testGetEpisode() throws Exception {        expect(remoteSimpsonServiceMock.getEpisode(17))            .andReturn(episode17Mock);        replay(remoteSimpsonServiceMock);        ISimpsonService clientSimpsonService =             new ClientSimpsonService(remoteSimpsonServiceMock);        IEpisode result = clientSimpsonService.getEpisode(17);        verify(remoteSimpsonServiceMock);        assertEquals(episode17Mock, result);    }

上文仅仅是抛砖引玉，想了解更多EasyMock，请参看

http://today.java.net/pub/a/today/2006/06/20/getting-started-with-easymock-2.html

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