JMock 簡介

接續 EasyMock 簡介，這邊改用另一套也為人所接受的Mock框架 JMock 來進行BookmarkDAO的模擬，如果搭配JUnit 3來進行撰寫：

package test.cc.openhome;

import org.jmock.Expectations;
import org.jmock.Mockery;
import java.util.Arrays;
import junit.framework.TestCase;
import cc.openhome.dao.BookmarkDAO;
import cc.openhome.model.Bookmark;
import cc.openhome.model.BookmarkService;

public class BookmarkServiceTest extends TestCase {
    private Bookmark bookmark1;
    private Bookmark bookmark2;
    private BookmarkDAO mockDAO;
    private BookmarkService service;
    
    private Mockery context;
    
    public void setUp() {
        bookmark1 = new Bookmark("testURL1", "testTitle1", "testCategory1");
        bookmark2 = new Bookmark("testURL2", "testTitle2", "testCategory2");
        
        context = new Mockery();
        // 建立Mock物件
        mockDAO = context.mock(BookmarkDAO.class);
        service = new BookmarkService(mockDAO);
    }
    
    public void testAddSameBookmark() {
        // 設定預期行為
        context.checking(new Expectations() {{
            // 會呼叫DAO的get()
            oneOf(mockDAO).get();
              will(returnValue(Arrays.asList(bookmark1))); // 預期傳回值 
        }});
        
        service.add(bookmark1);
    }
    
    public void testAddDifferentBookmark() {
        context.checking(new Expectations() {{
            oneOf(mockDAO).get(); 
              will(returnValue(Arrays.asList(bookmark1)));
            oneOf(mockDAO).add(bookmark2);
        }});
        
        service.add(bookmark2);
    }

    public void tearDown() {
        // 斷言是否滿足預期行為
        context.assertIsSatisfied();
    }
}

最主要的是在設定預期行為時，會遵照以下的形式：

呼叫次數(mock物件).方法(參數);
    inSequence(sequence名稱);
    when(狀態機.is(狀態));
    will(動作);
    then(狀態機.is(狀態));

呼叫次數如oneOf、atLeast.of等，例如至少呼叫過一次mockDAO的get，則可以這麼撰寫：

atLeast(1).of(mockDAO).get();

方法呼叫過後， inSequence、when、will、then都是可選擇性指定，以下例而言：
        context.checking(new Expectations() {{
            oneOf(mockDAO).get();
            will(returnValue(Arrays.asList(bookmark1)));
        }});

表示預期mockDAO會被呼叫get()一次，傳回包括bookmark1的List。在下面的程式碼中：
        context.checking(new Expectations() {{
            oneOf(mockDAO).get();
              will(returnValue(Arrays.asList(bookmark1)));
            oneOf(mockDAO).add(bookmark2);
        }});

呼叫get()、add()的順序並不要緊，如果你希望呼叫的順序一定是get()或add()，則可以設定Sequence，例如：
        final Sequence addDifferentBookmark =
      context.sequence("addDifferentBookmark");
        context.checking(new Expectations() {{
            oneOf(mockDAO).get();
              inSequence(addDifferentBookmark);
              will(returnValue(Arrays.asList(bookmark1)));
            oneOf(mockDAO).add(bookmark2);
              inSequence(addDifferentBookmark);
        }});

如果必須根據狀態而有對應的預期行為或切換狀態，則可以設定狀態機，以 JMock 官網文件上的例子來說：

final States pen = context.states("pen").startsAs("up");
...
oneOf(turtle).penDown();
    then(pen.is("down")); // penDown()呼叫過後狀態為down

oneOf(turtle).forward(10);
    when(pen.is("down")); // 只有在狀態為down時才呼叫forward()

oneOf(turtle).turn(90);
    when(pen.is("down"));

oneOf(turtle).forward(10);
    when(pen.is("down"));

oneOf(turtle).penUp();
    then(pen.is("up"));

如果搭配JUnit 4，可以如下撰寫：

package test.cc.openhome;

import org.jmock.Expectations;
import org.jmock.Mockery;
import org.jmock.Sequence;
import org.jmock.integration.junit4.JMock;
import org.jmock.integration.junit4.JUnit4Mockery;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import java.util.Arrays;
import cc.openhome.dao.BookmarkDAO;
import cc.openhome.model.Bookmark;
import cc.openhome.model.BookmarkService;

@RunWith(JMock.class)
public class BookmarkServiceTest {
    private Bookmark bookmark1;
    private Bookmark bookmark2;
    private BookmarkDAO mockDAO;
    private BookmarkService service;
    
    private Mockery context;
    
    @Before
    public void setUp() {
        bookmark1 = new Bookmark("testURL1", "testTitle1", "testCategory1");
        bookmark2 = new Bookmark("testURL2", "testTitle2", "testCategory2");
        
        context = new JUnit4Mockery();
        // 建立Mock物件
        mockDAO = context.mock(BookmarkDAO.class);
        service = new BookmarkService(mockDAO);
    }
    
    @Test
    public void testAddSameBookmark() {
        // 設定預期行為
        context.checking(new Expectations() {{
            // 會呼叫DAO的get()
            oneOf(mockDAO).get();
            // 預期傳回值
            will(returnValue(Arrays.asList(bookmark1)));
        }});
        
        service.add(bookmark1);
    }
    
    @Test
    public void testAddDifferentBookmark() {
        final Sequence addDifferentBookmark = 
            context.sequence("addDifferentBookmark");
        context.checking(new Expectations() {{
            oneOf(mockDAO).get();
              inSequence(addDifferentBookmark);
              will(returnValue(Arrays.asList(bookmark1)));
            oneOf(mockDAO).add(bookmark2);
              inSequence(addDifferentBookmark);
        }});
        
        service.add(bookmark2);
    }
}

使用JMock作為Runner，並搭配JUnit4Mockey，會在測試方法執行過後自動驗證行為是否正確。

JMock 官方網站提供了不少的文件可作為參考。