java單元測試之mock篇

• 一、什么是mock？
• 二、為什么要進(jìn)行mock？
• 三、IDEA中使用Mock
• • 3.1、引入mock所需依賴
  • 3.1、IDEA單元測試必備快捷鍵
  • 3.2、Mock測試相關(guān)注解
  • • • @Mock注解
      • @InjectMocks注解
      • 調(diào)用PowerMockito.spy()方法
      • Mock使用方式或者技巧
      • 靜態(tài)方法mockStatic
      • @PrepareForTest的使用場景
      • 阻止代碼初始化，包括static{}靜態(tài)代碼塊或者static變量的初始化
  • 3.3、問題

一、什么是mock？

Mock 測試就是在測試過程中，對于某些不容易構(gòu)造（如 HttpServletRequest 必須在Servlet 容器中才能構(gòu)造出來）或者不容易獲取的比較復(fù)雜的對象（如 JDBC 中的ResultSet 對象），用一個虛擬的對象（Mock 對象）來創(chuàng)建以便測試的測試方法。

二、為什么要進(jìn)行mock？

Mock是為了解決不同的單元之間由于耦合而難于開發(fā)、測試的問題。所以，Mock既能出現(xiàn)在單元測試中，也會出現(xiàn)在集成測試、系統(tǒng)測試過程中。Mock 最大的功能是幫你把單元測試的耦合分解開，如果你的代碼對另一個類或者接口有依賴，它能夠幫你模擬這些依賴，并幫你驗證所調(diào)用的依賴的行為。
比如一段代碼有這樣的依賴：

當(dāng)我們需要測試A類的時候，如果沒有 Mock，則我們需要把整個依賴樹都構(gòu)建出來，而使用 Mock 的話就可以將結(jié)構(gòu)分解開，像下面這樣：

三、IDEA中使用Mock

3.1、引入mock所需依賴

<dependency><groupId>org.mockito</groupId><artifactId>mockito-core</artifactId><version>3.9.0</version><scope>test</scope></dependency><dependency><groupId>org.powermock</groupId><artifactId>powermock-core</artifactId><version>2.0.9</version></dependency><dependency><groupId>org.powermock</groupId><artifactId>powermock-module-junit4</artifactId><version>2.0.9</version></dependency><dependency><groupId>org.powermock</groupId><artifactId>powermock-api-mockito2</artifactId><version>2.0.9</version><scope>test</scope></dependency>

3.1、IDEA單元測試必備快捷鍵

新建UT——Ctrl + Shift + T
雙擊所要進(jìn)行單元測試的類，點擊Ctrl + Shift + T,新建或者跳轉(zhuǎn)到已創(chuàng)建的UT，這里我們點擊Create New Test…新建UT，選擇JUnit4，選擇好需要測試的方法后點擊OK。

3.2、Mock測試相關(guān)注解

@Mock注解

@RunWith(PowerMockRunner.class) public class AnnouncementManagerImplTest {@MockAnnouncementMapper announcementMapper;@MockAnnouncementRepository announcementRepository;@InjectMocks@SpyAnnouncementManagerImpl announcementManagerImpl = new AnnouncementManagerImpl();@Beforepublic void before() {List<Announcement> res = new ArrayList<>();Announcement announcement = new Announcement();announcement.setId("dsfsdf");announcement.setAnnouncementContent("dsfbuiashf");res.add(announcement);PowerMockito.when(announcementMapper.queryByParams(Mockito.any(QueryWrapper.class), Mockito.any(Page.class))).thenReturn(res);PowerMockito.when(announcementMapper.selectCountByParams(Mockito.any(QueryWrapper.class))).thenReturn(1l);}@Testpublic void save() {}@Testpublic void findByPage() {QueryParams<AnnouncementDTO> params = new QueryParams<>();params.setPage(new Page(1,10));List<SortInfo> sort = new ArrayList<>();params.setSortInfo(sort);List<InputField> fields = new ArrayList<>();params.setParams(fields);IPage<Announcement> page = announcementManagerImpl.findByPage(params);Assert.assertNotNull(page.getTotal());Assert.assertNotNull(page.getRecords());} }

從上面代碼可以看出，被@Mock修飾后的變量announcementMapper則會產(chǎn)生一個AnnouncementMapper的mock類，不用@mock注解用mock方法來產(chǎn)生一個announcementMapper是一樣的效果。

@InjectMocks注解

@RunWith(PowerMockRunner.class) public class AnnouncementManagerImplTest {@MockAnnouncementMapper announcementMapper;@MockAnnouncementRepository announcementRepository;@InjectMocks@SpyAnnouncementManagerImpl announcementManagerImpl = new AnnouncementManagerImpl();@Beforepublic void before() {List<Announcement> res = new ArrayList<>();Announcement announcement = new Announcement();announcement.setId("dsfsdf");announcement.setAnnouncementContent("dsfbuiashf");res.add(announcement);PowerMockito.when(announcementMapper.queryByParams(Mockito.any(QueryWrapper.class), Mockito.any(Page.class))).thenReturn(res);PowerMockito.when(announcementMapper.selectCountByParams(Mockito.any(QueryWrapper.class))).thenReturn(1l);}@Testpublic void save() {}@Testpublic void findByPage() {QueryParams<AnnouncementDTO> params = new QueryParams<>();params.setPage(new Page(1,10));List<SortInfo> sort = new ArrayList<>();params.setSortInfo(sort);List<InputField> fields = new ArrayList<>();params.setParams(fields);IPage<Announcement> page = announcementManagerImpl.findByPage(params);Assert.assertNotNull(page.getTotal());Assert.assertNotNull(page.getRecords());} }

@InjectMocks注解修飾的類不能修飾抽象或接口類，被它修飾后，其被mock后的成員變量會注入
到@InjectMocks的類中。
比如上面的announcementMapper則會被注入到announcementManagerImpl中，當(dāng)調(diào)用announcementManagerImpl時，原代碼里的announcementMapper.selectCountByParams(queryWrapper)方法則會執(zhí)行mock方法

調(diào)用PowerMockito.spy()方法

通過spy,Whilebox.setInternelState方法設(shè)置內(nèi)部依賴

public class AnnouncementManagerImplTest {AnnouncementMapper announcementMapper;AnnouncementRepository announcementRepository;AnnouncementManagerImpl announcementManagerImpl;@Beforepublic void before() {MockitoAnnotations.openMocks(this);announcementManagerImpl = PowerMockito.spy(new AnnouncementManagerImpl());announcementMapper = PowerMockito.mock(AnnouncementMapper.class);Whitebox.setInternalState(announcementManagerImpl,"announcementMapper",announcementMapper);List<Announcement> res = new ArrayList<>();Announcement announcement = new Announcement();announcement.setId("dsfsdf");announcement.setAnnouncementContent("dsfbuiashf");res.add(announcement);PowerMockito.when(announcementMapper.queryByParams(Mockito.any(QueryWrapper.class), Mockito.any(Page.class))).thenReturn(res);PowerMockito.when(announcementMapper.selectCountByParams(Mockito.any(QueryWrapper.class))).thenReturn(1l);}@Testpublic void save() {}@Testpublic void findByPage() {QueryParams<AnnouncementDTO> params = new QueryParams<>();params.setPage(new Page(1,10));List<SortInfo> sort = new ArrayList<>();params.setSortInfo(sort);List<InputField> fields = new ArrayList<>();params.setParams(fields);IPage<Announcement> page = announcementManagerImpl.findByPage(params);Assert.assertNotNull(page.getTotal());Assert.assertNotNull(page.getRecords());} }

Mock使用方式或者技巧

在測試類上加注解@RunWith(PowerMockRunner.class)
等同于在@Before修飾的before方法中添加MockitoAnnotations.openMocks(this);

@Spy等同于PowerMockito.spy()方法

@Mock等同于PowerMockito.mock()方法

但是調(diào)用PowerMockito的方法時，必須要調(diào)用Whitebox.setInternalState()設(shè)置內(nèi)部依賴

靜態(tài)方法mockStatic

@RunWith(PowerMockRunner.class) @PrepareForTest(IdUtils.class) public class AnnouncementManagerImplTest {@MockAnnouncementMapper announcementMapper;@MockAnnouncementRepository announcementRepository;@InjectMocks@SpyAnnouncementManagerImpl announcementManagerImpl = new AnnouncementManagerImpl();@Beforepublic void before() {PowerMockito.mockStatic(IdUtils.class);List<Announcement> res = new ArrayList<>();Announcement announcement = new Announcement();announcement.setId("dsfsdf");announcement.setAnnouncementContent("dsfbuiashf");res.add(announcement);PowerMockito.when(IdUtils.randomUUID()).thenReturn("sahduiashdi");PowerMockito.when(announcementMapper.queryByParams(Mockito.any(QueryWrapper.class), Mockito.any(Page.class))).thenReturn(res);PowerMockito.when(announcementMapper.selectCountByParams(Mockito.any(QueryWrapper.class))).thenReturn(1l);}@Testpublic void save() {}@Testpublic void findByPage() {QueryParams<AnnouncementDTO> params = new QueryParams<>();params.setPage(new Page(1,10));List<SortInfo> sort = new ArrayList<>();params.setSortInfo(sort);List<InputField> fields = new ArrayList<>();params.setParams(fields);IPage<Announcement> page = announcementManagerImpl.findByPage(params);Assert.assertNotNull(page.getTotal());Assert.assertNotNull(page.getRecords());} }

當(dāng)需要mock靜態(tài)方法的時候，必須要加注解@PrepareForTest和@RunWith。注解@PrepareForTest里寫的類是靜態(tài)方法所在的類。
添加完注解再使用PowerMockito.mockStatic()方法，mock靜態(tài)類。

@PrepareForTest的使用場景

當(dāng)使用PowerMockito.whenNew方法時，必須加注解@PrepareForTest和@RunWith。注解@PrepareForTest里寫的類是需要mock的new對象代碼所在的類。

當(dāng)需要mock final方法的時候，必須加注解@PrepareForTest和@RunWith。注解@PrepareForTest里寫的類是final方法所在的類。

當(dāng)需要mock靜態(tài)方法的時候，必須加注解@PrepareForTest和@RunWith。注解@PrepareForTest里寫的類是靜態(tài)方法所在的類。

當(dāng)需要mock私有方法的時候, 只是需要加注解@PrepareForTest，注解里寫的類是私有方法所在的類

當(dāng)需要mock系統(tǒng)類的靜態(tài)方法的時候，必須加注解@PrepareForTest和@RunWith。注解里寫的類是需要調(diào)用系統(tǒng)方法所在的類

阻止代碼初始化，包括static{}靜態(tài)代碼塊或者static變量的初始化

@SuppressStaticInitializationFor("cn.com.jc.utils.IdUtils")

3.3、問題

1、使用@InjectMocks修飾接口類報錯

解決方法：
①收到new一個實現(xiàn)類的對象

@InjectMocksAnnouncementManager announcementManager = new AnnouncementManagerImpl();

②可以在@Before修飾的before()方法中添加spy方法注入該實現(xiàn)類對象

@InjectMocksAnnouncementManagerImpl announcementManager;@Beforepublic void before() {announcementManager = PowerMockito.spy(new AnnouncementManagerImpl());}

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