mockito简单教程

转自：http://blog.csdn.net/sdyy321/article/details/38757135/

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

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<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

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<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

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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

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@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

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@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);

}

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@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

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@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

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@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

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@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

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@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

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@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

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@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

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@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)

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@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：

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@Mock

private List mockList;

OK，我们再用注解的mock对象试试

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@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

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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

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@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

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@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

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@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

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@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

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@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

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@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

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@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

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@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());

}