Mockito教程

我会带着你远行 2022-03-10 10:48 320阅读 0赞

**目录**

1 [Mockito 介绍][Mockito]   
  1.1 [Mockito是什么？][Mockito 1]  
  1.2 [为什么需要Mock][Mock]  
  1.3 [Stub和Mock异同][Mock]  
  1.4 [Mockito资源][Mockito 2]  
  1.5 [使用场景][Link 1]  
2 [使用Mockito ][Mockito 3]  
  2.1[ 验证行为][Link 2]  
  2.2 [模拟我们所期望的结果][Link 3]  
  2.3 [RETURNS\_SMART\_NULLS和RETURNS\_DEEP\_STUBS][RETURNS_SMART_NULLS_RETURNS_DEEP_STUBS]  
  2.4 [模拟方法体抛出异常][Link 4]  
  2.5 [使用注解来快速模拟 ][Link 5]  
  2.6 [参数匹配][Link 6]  
  2.7 [自定义参数匹配][Link 7]  
  2.8 [捕获参数来进一步断言][Link 8]  
  2.9 [使用方法预期回调接口生成期望值（Answer结构）][Answer]  
  2.10 [修改对未预设的调用返回默认期望][Link 9]  
  2.11 [用spy监控真实对象][spy]    
  2.12 [真实的部分mock][mock]  
  2.13 [重置mock][mock 1]  
  2.14 [验证确切的调用次数][Link 10]  
  2.15 [连续调用][Link 11]  
  2.16 [验证执行顺序][Link 12]  
  2.17 [确保模拟对象上无互动发生][Link 13]  
  2.18 [找出冗余的互动(即未被验证到的)][Link 14]  
3 [Mockito如何实现Mock][Mockito_Mock]  
[参考][Link 15]

## 1 Mockito 介绍 \[3\] ##

--------------------

[返回][Link 16]

### 1.1 Mockito是什么？ ###

Mockito是mocking框架，它让你用简洁的API做测试。而且Mockito简单易学，它可读性强和验证语法简洁。

### 1.2 为什么需要Mock ###

测试驱动的开发( TDD)要求我们先写单元测试，再写实现代码。在写单元测试的过程中，我们往往会遇到要测试的类有很多依赖，这些依赖的类/对象/资源又有别的依赖，从而形成一个大的依赖树，要在单元测试的环境中完整地构建这样的依赖，是一件很困难的事情。如下图所示：

![484791-20170120134044703-96948251.png][]

为了测试类A，我们需要Mock B类和C类（用虚拟对象来代替）如下图所示：

![484791-20170120134311703-125872357.png][]

### 1.3 Stub和Mock异同\[1\] ###

*  相同：Stub和Mock都是模拟外部依赖
 *  不同：Stub是完全模拟一个外部依赖， 而Mock还可以用来判断测试通过还是失败

### 1.4 Mockito资源 ###

*  官网： [http://mockito.org][http_mockito.org]
 *  API文档：[http://docs.mockito.googlecode.com/hg/org/mockito/Mockito.html][http_docs.mockito.googlecode.com_hg_org_mockito_Mockito.html]
 *  项目源码：[https://github.com/mockito/mockito][https_github.com_mockito_mockito]

### 1.5 使用场景 ###

*  提前创建测试; TDD（测试驱动开发）
 *  团队可以并行工作
 *  你可以创建一个验证或者演示程序
 *  为无法访问的资源编写测试
 *  Mock 可以交给用户
 *  隔离系统

## 2 使用Mockito \[2\]\[4\] ##

--------------------

[返回][Link 16]

添加maven依赖

<dependency>
              <groupId>org.mockito</groupId>
              <artifactId>mockito-all</artifactId>
              <version>1.9.5</version>
              <scope>test</scope>
          </dependency>

添加junit依赖

<dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
          </dependency>

添加引用

import static org.mockito.Mockito.*;
    import static org.junit.Assert.*;

### 2.1 验证行为 ###

@Test
        public void verify_behaviour(){
            //模拟创建一个List对象
            List mock = mock(List.class);
            //使用mock的对象
            mock.add(1);
            mock.clear();
            //验证add(1)和clear()行为是否发生
            verify(mock).add(1);
            verify(mock).clear();
        }

### 2.2 模拟我们所期望的结果 ###

@Test
        public void when_thenReturn(){
            //mock一个Iterator类
            Iterator iterator = mock(Iterator.class);
            //预设当iterator调用next()时第一次返回hello，第n次都返回world
            when(iterator.next()).thenReturn("hello").thenReturn("world");
            //使用mock的对象
            String result = iterator.next() + " " + iterator.next() + " " + iterator.next();
            //验证结果
            assertEquals("hello world world",result);
        }

@Test(expected = IOException.class)
        public void when_thenThrow() throws IOException {
            OutputStream outputStream = mock(OutputStream.class);
            OutputStreamWriter writer = new OutputStreamWriter(outputStream);
            //预设当流关闭时抛出异常
            doThrow(new IOException()).when(outputStream).close();
            outputStream.close();
        }

### 2.3 RETURNS\_SMART\_NULLS和RETURNS\_DEEP\_STUBS ###

RETURNS\_SMART\_NULLS实现了Answer接口的对象，它是创建mock对象时的一个可选参数，mock(Class,Answer)。

在创建mock对象时，有的方法我们没有进行stubbing，所以调用时会放回Null这样在进行操作是很可能抛出NullPointerException。如果通过RETURNS\_SMART\_NULLS参数创建的mock对象在没有调用stubbed方法时会返回SmartNull。例如：返回类型是String，会返回"";是int，会返回0；是List，会返回空的List。另外，在控制台窗口中可以看到SmartNull的友好提示。

@Test
        public void returnsSmartNullsTest() {
            List mock = mock(List.class, RETURNS_SMART_NULLS);
            System.out.println(mock.get(0));
            
            //使用RETURNS_SMART_NULLS参数创建的mock对象，不会抛出NullPointerException异常。另外控制台窗口会提示信息“SmartNull returned by unstubbed get() method on mock”
            System.out.println(mock.toArray().length);
        }

RETURNS\_DEEP\_STUBS也是创建mock对象时的备选参数

RETURNS\_DEEP\_STUBS参数程序会自动进行mock所需的对象，方法deepstubsTest和deepstubsTest2是等价的

@Test
        public void deepstubsTest(){
            Account account=mock(Account.class,RETURNS_DEEP_STUBS);
            when(account.getRailwayTicket().getDestination()).thenReturn("Beijing");
            account.getRailwayTicket().getDestination();
            verify(account.getRailwayTicket()).getDestination();
            assertEquals("Beijing",account.getRailwayTicket().getDestination());
        }
        @Test
        public void deepstubsTest2(){
            Account account=mock(Account.class); 
            RailwayTicket railwayTicket=mock(RailwayTicket.class);        
            when(account.getRailwayTicket()).thenReturn(railwayTicket); 
            when(railwayTicket.getDestination()).thenReturn("Beijing");
            
            account.getRailwayTicket().getDestination();
            verify(account.getRailwayTicket()).getDestination();    
            assertEquals("Beijing",account.getRailwayTicket().getDestination());
        }    
        
        public class RailwayTicket{
            private String destination;
    
            public String getDestination() {
                return destination;
            }
    
            public void setDestination(String destination) {
                this.destination = destination;
            }        
        }
        
        public class Account{
            private RailwayTicket railwayTicket;
    
            public RailwayTicket getRailwayTicket() {
                return railwayTicket;
            }
    
            public void setRailwayTicket(RailwayTicket railwayTicket) {
                this.railwayTicket = railwayTicket;
            }
        }

### 2.4 模拟方法体抛出异常 ###

@Test(expected = RuntimeException.class)
        public void doThrow_when(){
            List list = mock(List.class);
            doThrow(new RuntimeException()).when(list).add(1);
            list.add(1);
        }

### 2.5 使用注解来快速模拟  ###

在上面的测试中我们在每个测试方法里都mock了一个List对象，为了避免重复的mock，是测试类更具有可读性，我们可以使用下面的注解方式来快速模拟对象：

@Mock
        private List mockList;
    OK，我们再用注解的mock对象试试 
    
        @Test
        public void shorthand(){
            mockList.add(1);
            verify(mockList).add(1);
        }

运行这个测试类你会发现报错了，mock的对象为NULL，为此我们必须在基类中添加初始化mock的代码

public class MockitoExample2 {
        @Mock
        private List mockList;
    
        public MockitoExample2(){
            MockitoAnnotations.initMocks(this);
        }
    
        @Test
        public void shorthand(){
            mockList.add(1);
            verify(mockList).add(1);
        }
    }

或者使用built-in runner：MockitoJUnitRunner

@RunWith(MockitoJUnitRunner.class)
    public class MockitoExample2 {
        @Mock
        private List mockList;
    
        @Test
        public void shorthand(){
            mockList.add(1);
            verify(mockList).add(1);
        }
    }

### 2.6 参数匹配 ###

@Test
        public void with_arguments(){
            Comparable comparable = mock(Comparable.class);
            //预设根据不同的参数返回不同的结果
            when(comparable.compareTo("Test")).thenReturn(1);
            when(comparable.compareTo("Omg")).thenReturn(2);
            assertEquals(1, comparable.compareTo("Test"));
            assertEquals(2, comparable.compareTo("Omg"));
            //对于没有预设的情况会返回默认值
            assertEquals(0, comparable.compareTo("Not stub"));
        }

除了匹配制定参数外，还可以匹配自己想要的任意参数

@Test
        public void with_unspecified_arguments(){
            List list = mock(List.class);
            //匹配任意参数
            when(list.get(anyInt())).thenReturn(1);
            when(list.contains(argThat(new IsValid()))).thenReturn(true);
            assertEquals(1, list.get(1));
            assertEquals(1, list.get(999));
            assertTrue(list.contains(1));
            assertTrue(!list.contains(3));
        }
    
        private class IsValid extends ArgumentMatcher<List>{
            @Override
            public boolean matches(Object o) {
                return o == 1 || o == 2;
            }
        }

注意：如果你使用了参数匹配，那么所有的参数都必须通过matchers来匹配，如下代码：

@Test
        public void all_arguments_provided_by_matchers(){
            Comparator comparator = mock(Comparator.class);
            comparator.compare("nihao","hello");
            //如果你使用了参数匹配，那么所有的参数都必须通过matchers来匹配
            verify(comparator).compare(anyString(),eq("hello"));
            //下面的为无效的参数匹配使用
            //verify(comparator).compare(anyString(),"hello");
        }

### 2.7 自定义参数匹配 ###

@Test
        public void argumentMatchersTest(){
            //创建mock对象
            List<String> mock = mock(List.class);
    
            //argThat(Matches<T> matcher)方法用来应用自定义的规则，可以传入任何实现Matcher接口的实现类。
            when(mock.addAll(argThat(new IsListofTwoElements()))).thenReturn(true);
    
            mock.addAll(Arrays.asList("one","two","three"));
            //IsListofTwoElements用来匹配size为2的List，因为例子传入List为三个元素，所以此时将失败。
            verify(mock).addAll(argThat(new IsListofTwoElements()));
        }
        
        class IsListofTwoElements extends ArgumentMatcher<List>
        {
            public boolean matches(Object list)
            {
                return((List)list).size()==2;
            }
        }

### 2.8 捕获参数来进一步断言 ###

较复杂的参数匹配器会降低代码的可读性，有些地方使用参数捕获器更加合适。

@Test
        public void capturing_args(){
            PersonDao personDao = mock(PersonDao.class);
            PersonService personService = new PersonService(personDao);
    
            ArgumentCaptor<Person> argument = ArgumentCaptor.forClass(Person.class);
            personService.update(1,"jack");
            verify(personDao).update(argument.capture());
            assertEquals(1,argument.getValue().getId());
            assertEquals("jack",argument.getValue().getName());
        }
    
         class Person{
            private int id;
            private String name;
    
            Person(int id, String name) {
                this.id = id;
                this.name = name;
            }
    
            public int getId() {
                return id;
            }
    
            public String getName() {
                return name;
            }
        }
    
        interface PersonDao{
            public void update(Person person);
        }
    
        class PersonService{
            private PersonDao personDao;
    
            PersonService(PersonDao personDao) {
                this.personDao = personDao;
            }
    
            public void update(int id,String name){
                personDao.update(new Person(id,name));
            }
        }

### 2.9 使用方法预期回调接口生成期望值（Answer结构） ###

@Test
        public void answerTest(){
            when(mockList.get(anyInt())).thenAnswer(new CustomAnswer());
            assertEquals("hello world:0",mockList.get(0));
            assertEquals("hello world:999",mockList.get(999));
        }
    
        private class CustomAnswer implements Answer<String>{
            @Override
            public String answer(InvocationOnMock invocation) throws Throwable {
                Object[] args = invocation.getArguments();
                return "hello world:"+args[0];
            }
        }

也可使用匿名内部类实现

@Test
        public void answer_with_callback(){
            //使用Answer来生成我们我们期望的返回
            when(mockList.get(anyInt())).thenAnswer(new Answer<Object>() {
                @Override
                public Object answer(InvocationOnMock invocation) throws Throwable {
                    Object[] args = invocation.getArguments();
                    return "hello world:"+args[0];
                }
            });
            assertEquals("hello world:0",mockList.get(0));
            assertEquals("hello world:999",mockList.get(999));
        }

### 2.10 修改对未预设的调用返回默认期望 ###

@Test
        public void unstubbed_invocations(){
            //mock对象使用Answer来对未预设的调用返回默认期望值
            List mock = mock(List.class,new Answer() {
                @Override
                public Object answer(InvocationOnMock invocation) throws Throwable {
                    return 999;
                }
            });
            //下面的get(1)没有预设，通常情况下会返回NULL，但是使用了Answer改变了默认期望值
            assertEquals(999, mock.get(1));
            //下面的size()没有预设，通常情况下会返回0，但是使用了Answer改变了默认期望值
            assertEquals(999,mock.size());
        }

### 2.11 用spy监控真实对象   ###

*  Mock不是真实的对象，它只是用类型的class创建了一个虚拟对象，并可以设置对象行为
 *  Spy是一个真实的对象，但它可以设置对象行为
 *  InjectMocks创建这个类的对象并自动将标记@Mock、@Spy等注解的属性值注入到这个中

@Test(expected = IndexOutOfBoundsException.class)
        public void spy_on_real_objects(){
            List list = new LinkedList();
            List spy = spy(list);
            //下面预设的spy.get(0)会报错，因为会调用真实对象的get(0)，所以会抛出越界异常
            //when(spy.get(0)).thenReturn(3);
    
            //使用doReturn-when可以避免when-thenReturn调用真实对象api
            doReturn(999).when(spy).get(999);
            //预设size()期望值
            when(spy.size()).thenReturn(100);
            //调用真实对象的api
            spy.add(1);
            spy.add(2);
            assertEquals(100,spy.size());
            assertEquals(1,spy.get(0));
            assertEquals(2,spy.get(1));
            verify(spy).add(1);
            verify(spy).add(2);
            assertEquals(999,spy.get(999));
            spy.get(2);
        }

### 2.12 真实的部分mock ###

@Test
        public void real_partial_mock(){
            //通过spy来调用真实的api
            List list = spy(new ArrayList());
            assertEquals(0,list.size());
            A a  = mock(A.class);
            //通过thenCallRealMethod来调用真实的api
            when(a.doSomething(anyInt())).thenCallRealMethod();
            assertEquals(999,a.doSomething(999));
        }
    
    
        class A{
            public int doSomething(int i){
                return i;
            }
        }

### 2.13 重置mock ###

@Test
        public void reset_mock(){
            List list = mock(List.class);
            when(list.size()).thenReturn(10);
            list.add(1);
            assertEquals(10,list.size());
            //重置mock，清除所有的互动和预设
            reset(list);
            assertEquals(0,list.size());
        }

### 2.14 验证确切的调用次数 ###

@Test
        public void verifying_number_of_invocations(){
            List list = mock(List.class);
            list.add(1);
            list.add(2);
            list.add(2);
            list.add(3);
            list.add(3);
            list.add(3);
            //验证是否被调用一次，等效于下面的times(1)
            verify(list).add(1);
            verify(list,times(1)).add(1);
            //验证是否被调用2次
            verify(list,times(2)).add(2);
            //验证是否被调用3次
            verify(list,times(3)).add(3);
            //验证是否从未被调用过
            verify(list,never()).add(4);
            //验证至少调用一次
            verify(list,atLeastOnce()).add(1);
            //验证至少调用2次
            verify(list,atLeast(2)).add(2);
            //验证至多调用3次
            verify(list,atMost(3)).add(3);
        }

### 2.15 连续调用 ###

@Test(expected = RuntimeException.class)
        public void consecutive_calls(){
            //模拟连续调用返回期望值，如果分开，则只有最后一个有效
            when(mockList.get(0)).thenReturn(0);
            when(mockList.get(0)).thenReturn(1);
            when(mockList.get(0)).thenReturn(2);
            when(mockList.get(1)).thenReturn(0).thenReturn(1).thenThrow(new RuntimeException());
            assertEquals(2,mockList.get(0));
            assertEquals(2,mockList.get(0));
            assertEquals(0,mockList.get(1));
            assertEquals(1,mockList.get(1));
            //第三次或更多调用都会抛出异常
            mockList.get(1);
        }

### 2.16 验证执行顺序 ###

@Test
        public void verification_in_order(){
            List list = mock(List.class);
            List list2 = mock(List.class);
            list.add(1);
            list2.add("hello");
            list.add(2);
            list2.add("world");
            //将需要排序的mock对象放入InOrder
            InOrder inOrder = inOrder(list,list2);
            //下面的代码不能颠倒顺序，验证执行顺序
            inOrder.verify(list).add(1);
            inOrder.verify(list2).add("hello");
            inOrder.verify(list).add(2);
            inOrder.verify(list2).add("world");
        }

### 2.17 确保模拟对象上无互动发生 ###

@Test
        public void verify_interaction(){
            List list = mock(List.class);
            List list2 = mock(List.class);
            List list3 = mock(List.class);
            list.add(1);
            verify(list).add(1);
            verify(list,never()).add(2);
            //验证零互动行为
            verifyZeroInteractions(list2,list3);
        }

### 2.18 找出冗余的互动(即未被验证到的) ###

@Test(expected = NoInteractionsWanted.class)
        public void find_redundant_interaction(){
            List list = mock(List.class);
            list.add(1);
            list.add(2);
            verify(list,times(2)).add(anyInt());
            //检查是否有未被验证的互动行为，因为add(1)和add(2)都会被上面的anyInt()验证到，所以下面的代码会通过
            verifyNoMoreInteractions(list);
    
            List list2 = mock(List.class);
            list2.add(1);
            list2.add(2);
            verify(list2).add(1);
            //检查是否有未被验证的互动行为，因为add(2)没有被验证，所以下面的代码会失败抛出异常
            verifyNoMoreInteractions(list2);
        }

## 3 Mockito如何实现Mock\[3\] ##

--------------------

[返回][Link 16]

Mockito并不是创建一个真实的对象，而是模拟这个对象，他用简单的when(mock.method(params)).thenRetrun(result)语句设置mock对象的行为，如下语句：

// 设置mock对象的行为 － 当调用其get方法获取第0个元素时，返回"first"
    Mockito.when(mockedList.get(0)).thenReturn("first");

在Mock对象的时候，创建一个proxy对象，保存被调用的方法名（get），以及调用时候传递的参数（0），然后在调用thenReturn方法时再把“first”保存起来，这样，就有了构建一个stub方法所需的所有信息，构建一个stub。当get方法被调用的时候，实际上调用的是之前保存的proxy对象的get方法，返回之前保存的数据。

## 参考 ##

\[1\] [单元测试之Stub和Mock][Stub_Mock]

\[2\] [mockito简单教程][mockito]

\[3\] [Mockito入门][Mockito 4]

\[4\] [学习Mockito][Mockito 5]

原文：[https://www.cnblogs.com/Ming8006/p/6297333.html][https_www.cnblogs.com_Ming8006_p_6297333.html]

[Mockito]: https://www.cnblogs.com/Ming8006/p/6297333.html#c1
[Mockito 1]: https://www.cnblogs.com/Ming8006/p/6297333.html#c1.1
[Mock]: https://www.cnblogs.com/Ming8006/p/6297333.html#c1.3
[Mockito 2]: https://www.cnblogs.com/Ming8006/p/6297333.html#c1.4
[Link 1]: https://www.cnblogs.com/Ming8006/p/6297333.html#c1.5
[Mockito 3]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2
[Link 2]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.1
[Link 3]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.2
[RETURNS_SMART_NULLS_RETURNS_DEEP_STUBS]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.3
[Link 4]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.4
[Link 5]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.5
[Link 6]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.6
[Link 7]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.7
[Link 8]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.8
[Answer]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.9
[Link 9]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.10
[spy]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.11
[mock]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.12
[mock 1]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.13
[Link 10]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.14
[Link 11]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.15
[Link 12]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.16
[Link 13]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.17
[Link 14]: https://www.cnblogs.com/Ming8006/p/6297333.html#c2.18
[Mockito_Mock]: https://www.cnblogs.com/Ming8006/p/6297333.html#c3
[Link 15]: https://www.cnblogs.com/Ming8006/p/6297333.html#c4
[Link 16]: https://www.cnblogs.com/Ming8006/p/6297333.html#top
[484791-20170120134044703-96948251.png]: /images/20220310/112ee80b0ef14623a61dccad7ccd1142.png
[484791-20170120134311703-125872357.png]: /images/20220310/bd20cafc19d641dfbe30d766c7674411.png
[http_mockito.org]: http://mockito.org/
[http_docs.mockito.googlecode.com_hg_org_mockito_Mockito.html]: http://docs.mockito.googlecode.com/hg/org/mockito/Mockito.html
[https_github.com_mockito_mockito]: https://github.com/mockito/mockito
[Stub_Mock]: http://www.cnblogs.com/TankXiao/archive/2012/03/06/2366073.html#diff
[mockito]: http://blog.csdn.net/sdyy321/article/details/38757135/
[Mockito 4]: http://blog.csdn.net/jhg19900321/article/details/49531983
[Mockito 5]: http://wenku.baidu.com/view/8def451a227916888486d73f.html
[https_www.cnblogs.com_Ming8006_p_6297333.html]: https://www.cnblogs.com/Ming8006/p/6297333.html