Easymock之初见

准本工作：

从easymock3版本之后，可以同时mock接口和类，不再需要extention class 包了。使用easymock需要依赖两个包，分别是 Objenesis 和 Cglib

基本概念：

一 . mock和stub的相同点和不同点?

在Manning Junit in Action一书中是这样描述的：

Mocks replace the objects with which your methods
under test collaborate, offering a layer of isolation. In that sense, they’re similar to stubs. But
this is where the similarity ends, because mocks don’t implement any logic: they’re empty shells that provide methods to let the tests control
the behavior of all the business methods of the faked class.

详细的来讲

1.相同点：mock和stub都可以用来对系统(或者将粒度放小为模块，单元)进行隔离。

2.不同点：待补充

Lifecycle

Test lifecycle with stubs:

Setup - Prepare object that is being tested and its stubs collaborators.

Exercise - Test the functionality.

Verify state - Use asserts to check object's state.

Teardown - Clean up resources.

Test lifecycle with mocks:

Setup data - Prepare object that is being tested.

Setup expectations - Prepare expectations in mock that is being used by primary object.

Exercise - Test the functionality.

Verify expectations - Verify that correct methods has been invoked in mock.

Verify state - Use asserts to check object's state.

Teardown - Clean up resources.

三.easymock的基本用法

mock一般都有三个阶段，分别是 record，replay，verify。即首先记录mock对象上的操作，然后重演这些操作，最后验证这些操作。

在mock对象调用replay()方法之前是记录mock上的操作阶段。在调用replay()方法之后，才表现出mock对象的行为，并检查这些期望的操作是否真正的被调用。

要获得一个Mock对象，需要三个步骤：

使用接口创建一个mock对象
记录期望的行为(record the expected behavior)
将mock对象切换到replay状态，重演期望的行为

下面使用一个最常用的例子来展示一下mock的基本用法：

实体类User，DAO层接口UserDao，Service层接口UserService，测试对象Service的各个方法是否正确，service所需依赖UserDao，所以需要mock出UserDao对象，用来隔离层，专注于service层的单元测试。类图如下：





User对象：

public class User {
private int id;
private String name;
private String age;
public User(){}
public User(int id,String name,String age){
this.id=id;
this.name=name;
this.age=age;
}
//省略getter and setter方法
public void say(){
System.out.println(String.format("%d %s %s ",id,name,age));
}
}

UserDao接口：

public interface UserDao {
User getUserById(int id);
int count();
public String getUserAddress() throws Exception;
}

UserService类，注意这里为了简单，没有使用接口，而是直接使用类代替

public class UserService {
private UserDao userDao;

public UserDao getUserDao() {
return userDao;
}

public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}

public String getUserNameById(int id){
String username=userDao.getUserById(id).getName();
return username;
}

public int count(){
return userDao.count();
}
public User getUser(int id){
return userDao.getUserById(id);
}
public String getUserAddress(int id) throws Exception{
return userDao.getUserAddress();
}
}

接下来是主要的测试代码：

package easymock;

import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

import static org.easymock.EasyMock.*;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

/**
* Created by superman on 14-1-12.
*/
public class UserServiceTest {
private UserService userService;
private UserDao userDaoMock;
private User user;
@Before
public void setUp(){
user=new User(1,"tom","20");
userService=new UserService();
userDaoMock=createMock(UserDao.class);
}
@Test
public void testGetNameById(){
expect(userDaoMock.getUserById(1)).andReturn(user);
replay(userDaoMock);

userService.setUserDao(userDaoMock);

String name=userService.getUserNameById(1);
assertEquals("tom",name);
verify(userDaoMock);
}
@Test
public void testRepeateCall(){
expect(userDaoMock.getUserById(1)).andReturn(user).times(2);
replay(userDaoMock);
userService.setUserDao(userDaoMock);

String name=userService.getUserNameById(1);
name=userService.getUserNameById(1);
verify(userDaoMock);
assertEquals("tom",name);
}
@Test
public void testReturnValue(){
//        expect(userDaoMock.getUserById(1)).andReturn(user);
userDaoMock.getUserById(lt(2));
expectLastCall().andReturn(user);

replay(userDaoMock);
userService.setUserDao(userDaoMock);
User user=userService.getUser(1);
assertNotNull(user);
verify(userDaoMock);
}
@Test
@Ignore
public void testException(){
try {
expect(userDaoMock.getUserAddress()).andThrow(new Exception("no address attribute"));
replay(userDaoMock);
userService.setUserDao(userDaoMock);
userService.getUserAddress(1);
verify(userDaoMock);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Tip：mock创建的构造方法

createMock(String name, Class claz);

createMock(Class claz);

如果使用第二种，如果测试结果没有预期的，那么会出现如下提示：

java.lang.AssertionError:
Expectation failure on verify:
read(): expected: 7, actual: 0

如果使用第一种，则会出现如下提示:

java.lang.AssertionError:
Expectation failure on verify:
name.read(): expected: 7, actual: 0

红色部分是区别，所以使用第一种更好，标注了提示。

测试代码主要参考：http://easymock.org/EasyMock3_0_Documentation.html