mockito简单教程

转载：http://blog.csdn.net/u012881904/article/details/51334747

官网： http://mockito.org

API文档：http://docs.mockito.googlecode.com/hg/org/mockito/Mockito.html

项目源码：https://github.com/mockito/mockito

首先添加maven依赖

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

当然mockito需要junit配合使用

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

然后为了使代码更简洁，最好在测试类中导入静态资源

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

下面我们开始使用mockito来做测试

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、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();
}

3、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;
    }
}

需要注意的是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

@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");
}

4、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);
</span>}

5、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);
}

6、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");
}

7、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);
}

8、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);
}

9、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);
    }
}

更多的注解还有@Captor,@Spy,@InjectMocks

10、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);
}

11、使用回调生成期望值

@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));
}

12、监控真实对象

使用spy来监控真实的对象，需要注意的是此时我们需要谨慎的使用when-then语句，而改用do-when语句

@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);
}

13、修改对未预设的调用返回默认期望值

@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());
}

14、捕获参数来进一步断言

       @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));
    }
}

15、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;
    }
}

16、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());
}