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