本文轉自http://www.cnblogs.com/Ming8006/p/6297333.html#c1,並對測試不通過的case做了修改,以便能在java 1.8上執行。
1 Mockito 介紹 [3]
1.1 Mockito是什麼?
Mockito是mocking框架,它讓你用簡潔的API做測試。而且Mockito簡單易學,它可讀性強和驗證語法簡潔。
1.2 爲什麼需要Mock
測試驅動的開發( TDD)要求我們先寫單元測試,再寫實現代碼。在寫單元測試的過程中,我們往往會遇到要測試的類有很多依賴,這些依賴的類/對象/資源又有別的依賴,從而形成一個大的依賴樹,要在單元測試的環境中完整地構建這樣的依賴,是一件很困難的事情。如下圖所示:
爲了測試類A,我們需要Mock B類和C類(用虛擬對象來代替)如下圖所示:
1.3 Stub和Mock異同[1]
- 相同:Stub和Mock都是模擬外部依賴
- 不同:Stub是完全模擬一個外部依賴, 而Mock還可以用來判斷測試通過還是失敗
1.4 Mockito資源
- 官網: http://mockito.org
- API文檔:http://docs.mockito.googlecode.com/hg/org/mockito/Mockito.html
- 項目源碼:https://github.com/mockito/mockito
1.5 使用場景
- 提前創建測試; TDD(測試驅動開發)
- 團隊可以並行工作
- 你可以創建一個驗證或者演示程序
- 爲無法訪問的資源編寫測試
- Mock 可以交給用戶
- 隔離系統
2 使用Mockito [2][4]
添加maven依賴
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>2.23.4</version>
<scope>test</scope>
</dependency>
添加junit依賴
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
添加引用
import org.junit.Test;
import org.mockito.ArgumentCaptor;
import org.mockito.ArgumentMatcher;
import org.mockito.InOrder;
import org.mockito.exceptions.verification.NoInteractionsWanted;
import org.mockito.exceptions.verification.junit.ArgumentsAreDifferent;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import static org.mockito.Mockito.*;
import static org.mockito.Mockito.mock;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
2.1 驗證行爲
@Test
public void verify_behaviour(){
//模擬創建一個List對象
List mock = mock(List.class);
//使用mock的對象
mock.add(1);
mock.clear();
//驗證add(1)和clear()行爲是否發生
verify(mock).add(1);
verify(mock).clear();
}
2.2 模擬我們所期望的結果
@Test
public void when_thenReturn(){
//mock一個Iterator類
Iterator iterator = mock(Iterator.class);
//預設當iterator調用next()時第一次返回hello,第n次都返回world
when(iterator.next()).thenReturn("hello").thenReturn("world");
//使用mock的對象
String result = iterator.next() + " " + iterator.next() + " " + iterator.next();
//驗證結果
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);
//預設當流關閉時拋出異常
doThrow(new IOException()).when(outputStream).close();
outputStream.close();
}
2.3 RETURNS_SMART_NULLS和RETURNS_DEEP_STUBS
RETURNS_SMART_NULLS實現了Answer接口的對象,它是創建mock對象時的一個可選參數,mock(Class,Answer)。
在創建mock對象時,有的方法我們沒有進行stubbing,所以調用時會放回Null這樣在進行操作是很可能拋出NullPointerException。如果通過RETURNS_SMART_NULLS參數創建的mock對象在沒有調用stubbed方法時會返回SmartNull。例如:返回類型是String,會返回"";是int,會返回0;是List,會返回空的List。另外,在控制檯窗口中可以看到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參數創建的mock對象,不會拋出NullPointerException異常。另外控制檯窗口會提示信息“SmartNull returned by unstubbed get() method on mock”
System.out.println(mock.toArray().length);
}
RETURNS_DEEP_STUBS也是創建mock對象時的備選參數
RETURNS_DEEP_STUBS參數程序會自動進行mock所需的對象,方法deepstubsTest和deepstubsTest2是等價的
@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 模擬方法體拋出異常
@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 使用註解來快速模擬
在上面的測試中我們在每個測試方法裏都mock了一個List對象,爲了避免重複的mock,是測試類更具有可讀性,我們可以使用下面的註解方式來快速模擬對象:
@Mock
private List mockList;
OK,我們再用註解的mock對象試試
@Test
public void shorthand(){
mockList.add(1);
verify(mockList).add(1);
}
運行這個測試類你會發現報錯了,mock的對象爲NULL,爲此我們必須在基類中添加初始化mock的代碼
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 參數匹配
@Test
public void with_arguments(){
Comparable comparable = mock(Comparable.class);
//預設根據不同的參數返回不同的結果
when(comparable.compareTo("Test")).thenReturn(1);
when(comparable.compareTo("Omg")).thenReturn(2);
assertEquals(1, comparable.compareTo("Test"));
assertEquals(2, comparable.compareTo("Omg"));
//對於沒有預設的情況會返回默認值
assertEquals(0, comparable.compareTo("Not stub"));
}
除了匹配製定參數外,還可以匹配自己想要的任意參數
@Test
public void with_unspecified_arguments(){
List list = mock(List.class);
//匹配任意參數
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 implements ArgumentMatcher<Integer> {
@Override
public boolean matches(Integer o) {
return o == 1 || o == 2 ;
}
}
注意:如果你使用了參數匹配,那麼所有的參數都必須通過matchers來匹配,如下代碼:
@Test
public void all_arguments_provided_by_matchers(){
Comparator comparator = mock(Comparator.class);
comparator.compare("nihao","hello");
//如果你使用了參數匹配,那麼所有的參數都必須通過matchers來匹配
verify(comparator).compare(anyString(),eq("hello"));
//下面的爲無效的參數匹配使用
//verify(comparator).compare(anyString(),"hello");
}
2.7 自定義參數匹配
@Test (expected = ArgumentsAreDifferent.class)
public void argumentMatchersTest(){
//創建mock對象
List<String> mock = mock(List.class);
//argThat(Matches<T> matcher)方法用來應用自定義的規則,可以傳入任何實現Matcher接口的實現類。
when(mock.addAll(argThat(new IsListofTwoElements()))).thenReturn(true);
mock.addAll(Arrays.asList("one","two","three"));
//IsListofTwoElements用來匹配size爲2的List,因爲例子傳入List爲三個元素,所以此時將失敗。
verify(mock).addAll(argThat(new IsListofTwoElements()));
}
class IsListofTwoElements implements ArgumentMatcher<List>
{
public boolean matches(List list)
{
return(list).size()==2;
}
}
2.8 捕獲參數來進一步斷言
較複雜的參數匹配器會降低代碼的可讀性,有些地方使用參數捕獲器更加合適。
@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 使用方法預期回調接口生成期望值(Answer結構)
@Test
public void answerTest(){
List mockList = mock(List.class);
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];
}
}
也可使用匿名內部類實現
@Test
public void answer_with_callback(){
List mockList = mock(List.class);
//使用Answer來生成我們我們期望的返回
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 修改對未預設的調用返回默認期望
@Test
public void unstubbed_invocations(){
//mock對象使用Answer來對未預設的調用返回默認期望值
List mock = mock(List.class,new Answer() {
@Override
public Object answer(InvocationOnMock invocation) throws Throwable {
return 999;
}
});
//下面的get(1)沒有預設,通常情況下會返回NULL,但是使用了Answer改變了默認期望值
assertEquals(999, mock.get(1));
//下面的size()沒有預設,通常情況下會返回0,但是使用了Answer改變了默認期望值
assertEquals(999,mock.size());
}
2.11 用spy監控真實對象
- Mock不是真實的對象,它只是用類型的class創建了一個虛擬對象,並可以設置對象行爲
- Spy是一個真實的對象,但它可以設置對象行爲
- InjectMocks創建這個類的對象並自動將標記@Mock、@Spy等註解的屬性值注入到這個中
@Test(expected = IndexOutOfBoundsException.class)
public void spy_on_real_objects(){
List list = new LinkedList();
List spy = spy(list);
//下面預設的spy.get(0)會報錯,因爲會調用真實對象的get(0),所以會拋出越界異常
//when(spy.get(0)).thenReturn(3);
//使用doReturn-when可以避免when-thenReturn調用真實對象api
doReturn(999).when(spy).get(999);
//預設size()期望值
when(spy.size()).thenReturn(100);
//調用真實對象的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 真實的部分mock
@Test
public void real_partial_mock(){
//通過spy來調用真實的api
List list = spy(new ArrayList());
assertEquals(0,list.size());
A a = mock(A.class);
//通過thenCallRealMethod來調用真實的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,清除所有的互動和預設
reset(list);
assertEquals(0,list.size());
}
2.14 驗證確切的調用次數
@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);
//驗證是否被調用一次,等效於下面的times(1)
verify(list).add(1);
verify(list,times(1)).add(1);
//驗證是否被調用2次
verify(list,times(2)).add(2);
//驗證是否被調用3次
verify(list,times(3)).add(3);
//驗證是否從未被調用過
verify(list,never()).add(4);
//驗證至少調用一次
verify(list,atLeastOnce()).add(1);
//驗證至少調用2次
verify(list,atLeast(2)).add(2);
//驗證至多調用3次
verify(list,atMost(3)).add(3);
}
2.15 連續調用
@Test(expected = RuntimeException.class)
public void consecutive_calls(){
List mockList = mock(List.class);
//模擬連續調用返回期望值,如果分開,則只有最後一個有效
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));
//第三次或更多調用都會拋出異常
mockList.get(1);
}
2.16 驗證執行順序
@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");
//將需要排序的mock對象放入InOrder
InOrder inOrder = inOrder(list,list2);
//下面的代碼不能顛倒順序,驗證執行順序
inOrder.verify(list).add(1);
inOrder.verify(list2).add("hello");
inOrder.verify(list).add(2);
inOrder.verify(list2).add("world");
}
2.17 確保模擬對象上無互動發生
@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);
//驗證零互動行爲
verifyZeroInteractions(list2,list3);
}
2.18 找出冗餘的互動(即未被驗證到的)
@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());
//檢查是否有未被驗證的互動行爲,因爲add(1)和add(2)都會被上面的anyInt()驗證到,所以下面的代碼會通過
verifyNoMoreInteractions(list);
List list2 = mock(List.class);
list2.add(1);
list2.add(2);
verify(list2).add(1);
//檢查是否有未被驗證的互動行爲,因爲add(2)沒有被驗證,所以下面的代碼會失敗拋出異常
verifyNoMoreInteractions(list2);
}
3 Mockito如何實現Mock[3]
Mockito並不是創建一個真實的對象,而是模擬這個對象,他用簡單的when(mock.method(params)).thenRetrun(result)語句設置mock對象的行爲,如下語句:
// 設置mock對象的行爲 - 當調用其get方法獲取第0個元素時,返回"first"
Mockito.when(mockedList.get(0)).thenReturn("first");
在Mock對象的時候,創建一個proxy對象,保存被調用的方法名(get),以及調用時候傳遞的參數(0),然後在調用thenReturn方法時再把“first”保存起來,這樣,就有了構建一個stub方法所需的所有信息,構建一個stub。當get方法被調用的時候,實際上調用的是之前保存的proxy對象的get方法,返回之前保存的數據。
參考
[1] 單元測試之Stub和Mock
[2] mockito簡單教程
[3] Mockito入門
[4] 學習Mockito