使用PowerMock和Easymock進行單元測試
阿新 • • 發佈：2019-01-08
Java單元測試對於開發人員質量保證至關重要，尤其當面對一團亂碼的遺留程式碼時，沒有高覆蓋率的單元測試做保障，沒人敢輕易對程式碼進行重構。然而單元測試的編寫也不是一件容易的事情，除非使用TDD方式，否則編寫出容易測試的程式碼不但對開發人員的設計編碼要求很高，而且程式碼中的各種依賴也常常為單元測試帶來無窮無盡的障礙。令人欣慰的是開源社群各種優秀的Mock框架讓單元測試不再複雜，本文簡單介紹EasyMock，PowerMock等的基本常用用法。Mock說白了就是打樁（Stub）或則模擬，當你呼叫一個不好在測試中建立的物件時，Mock框架為你模擬一個和真實物件類似的替身來完成相應的行為。
EasyMock：
使用如下方式在Maven中新增EasyMock的依賴：
<dependency>
<groupId>org.easymock</groupId>
<artifactId>easymock</artifactId>
<version>3.2</version>
<scope>test</scope>
</dependency>EasyMock使用動態代理實現模擬物件建立，其基本步驟為以下四步：以資料庫應用為例的被測試程式碼如下：
現在希望對UserServiceImpl進行測試，而UserDao開發組只給出介面，尚未完成功能實現。使用Mock對UserDao進行模擬來測試UserServiceImpl。(1).基本的測試程式碼如下：public class UserServiceImpl{ private UserDao dao; public User query(String id) throws Exception{ try{ return dao.getById(id); }catch(Exception e){ throw e; } return null; } } public class UserDao{ public User getById(String id) throws Exception{ try{ return ……; }catch(Exception e){ throw e; } return null; } }
(2).呼叫測試設定：如果想測試UserServiceImpl呼叫了UserDao的getById方法3次，則使用如下程式碼即可：public class UserServiceImplTest { @Test public void testQuery() { User expectedUser = new User(); user.setId(“1001”); UserDao mock = EasyMock.createMock(UserDao.class);//建立Mock物件 Easymock.expect(mock.getById("1001")).andReturn(expectedUser);//錄製Mock物件預期行為 Easymock.replay(mock);//重放Mock物件，測試時以錄製的物件預期行為代替真實物件的行為 UserServiceImpl service = new UserServiceImpl(); service.setUserDao(mock); user user = service.query("1001");//呼叫測試方法 assertEquals(expectedUser, user); //斷言測試結果 Easymock.verify(mock);//驗證Mock物件被呼叫 } }
Easymock.expect(mock.getById("1001")).andReturn(exceptUser).times(3); Easymock.expect(mock.getById("1001")).andThrow(new RuntimeException());Easymock.expect(mock.getById(Easymock.isA(String.class))).andReturn(exceptedUser).times(3); public class UserServiceImpl{
private UserDao dao;
public List<String> queryNames(String[] ids) throws Exception{
try{
return dao.getNames(ids);
}catch(Exception e){
throw e;
}
return null;
}
}
public class UserDao{
public List<String> getNames(String[] ids) throws Exception{
try{
return ……;
}catch(Exception e){
throw e;
}
return null;
}
} Easymock.expect(mock.getNames(EasyMock.aryEq(testIds))).andReturn(exceptedNames); Easymock.expect(mock.getNames(EasyMock.isA(String[].class))).andReturn(exceptedNames); public class UserDao {
public void updateUserById(String id) throws Exception{
try{
update…
}catch(Exception e){
throw e;
}
}
} mock.updateUserById(“TestId”);
EasyMock.expectLastCall().anytimes(); mock.updateUserById(“TestId”);
EasyMock.expectLastCall().andThrow(new RuntimeException()).anytimes(); public List<String> getUserNames () throws Exception{
List<String> usernames = new ArrayList<String>();
ResultSet rs = pstmt.executeQuery(query);
try {
while(rs.next()){
usernames.add(rs.getString(2));
}
} catch (SQLException e) {
throw e;
}
} EasyMock.expect(rs.next()).andReturn(true).times(2).andReturn(false).times(1); PowerMock：
上面介紹的EasyMock可以滿足單元測試中的大部分需求，但是由於動態代理是使用了面向物件的繼承和多型特性，JDK自身的動態代理只針對介面進行代理，其本質是為介面生成一個實現類，而CGLIB可以針對類進行代理，其本質是將類自身作為基類。如果遇到了靜態、final型別的類和方法，以及私有方法，EasyMock的動態代理侷限性使得無法測試這些特性情況。PowerMock是在EasyMock基礎上進行擴充套件（只是補充，不是替代），使用了位元組碼操作技術直接對生成的位元組碼類檔案進行修改，從而可以方便對靜態，final型別的類和方法進行Mock，還可以對私有方法進行Mock，更可以對類進行部分Mock。PowerMock的工作過程和EasyMock類似，不同之處在於需要在類層次宣告@RunWith(PowerMockRunner.class)註解，以確保使用PowerMock框架引擎執行單元測試。通過如下方式在maven新增PowerMock相關依賴：
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-easymock</artifactId>
<version>1.5.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-module-junit4</artifactId>
<version>1.5.1</version>
<scope>test</scope>
</dependency>
public class SystemPropertyMockDemo {
public String getSystemProperty() throws IOException {
return System.getProperty("property");
}
} @RunWith(PowerMockRunner.class)
@PrepareForTest({SystemPropertyMockDemo.class})//宣告要Mock的類
public class SystemPropertyMockDemoTest {
@Test
public void demoOfFinalSystemClassMocking() throws Exception {
PowerMock.mockStatic(System.class);//Mock靜態方法
EasyMock.expect(System.getProperty("property")).andReturn("my property");//錄製Mock物件的靜態方法
PowerMock.replayAll();//重放Mock物件
Assert.assertEquals("my property",
new SystemPropertyMockDemo().getSystemProperty());
PowerMock.verifyAll();//驗證Mock物件
}
} <dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-mockito</artifactId>
<version>1.5.1</version>
<scope>test</scope>
</dependency> @RunWith(PowerMockRunner.class)
@PrepareForTest({SystemPropertyMockDemo.class})
public class SystemPropertyMockDemoTest {
@Test
public void demoOfFinalSystemClassMocking() throws Exception {
PowerMockito.mockStatic(System.class);
PowerMockito.when(System.getProperty("property")).thenReturn("my property");
PowerMock.replayAll();
Assert.assertEquals("my property",
new SystemPropertyMockDemo().getSystemProperty());
PowerMock.verifyAll();
}
} public class ClassDependency {
public final boolean isAlive() {
return false;
}
}
public class ClassUnderTest{
public boolean callFinalMethod(ClassDependency refer) {
return refer.isAlive();
}
} @RunWith(PowerMockRunner.class)
public class FinalMethodMockDemoTest {
@Test
@PrepareForTest(ClassDependency.class)
public void testCallFinalMethod() {
ClassDependency depencency = PowerMock.createMock(ClassDependency.class); //建立Mock物件
ClassUnderTest underTest = new ClassUnderTest();
EasyMock.expect(depencency.isAlive()).andReturn(true);
PowerMock.replayAll();
Assert.assertTrue(underTest.callFinalMethod(depencency));
PowerMock.verifyAll();
}
}
public class DataService {
public boolean replaceData(final String dataId, final byte[] binaryData) {
return modifyData(dataId, binaryData);
}
public boolean deleteData(final String dataId) {
return modifyData(dataId, null);
}
private boolean modifyData(final String dataId, final byte[] binaryData) {
return true;
}
} @RunWith(PowerMockRunner.class)
@PrepareForTest(DataService.class)
public class DataServiceTest {
@Test
public void testReplaceData() throws Exception {
DataService tested = PowerMock.createPartialMock(DataService.class, “modifyData”);//建立部分mock物件，只對modifyData方法Mock
PowerMock.expectPrivate(tested, “modifyData”, “id”, null).andReturn(true);//錄製私有方法
PowerMock.replay(tested);
assertTrue(tested.deleteData(“id”));
PowerMock.verify(tested);
}
}
public class PersistenceManager {
public boolean createDirectoryStructure(String directoryPath) {
File directory = new File(directoryPath);
if (directory.exists()) {
throw new IllegalArgumentException("\"" + directoryPath + "\" already exists.");
}
return directory.mkdirs();
}
} @RunWith(PowerMockRunner.class)
@PrepareForTest( PersistenceManager.class )
public class PersistenceManagerTest {
@Test
public void testCreateDirectoryStructure_ok() throws Exception {
File fileMock = PowerMock.createMock(File.class);
PersistenceManager tested = new PersistenceManager();
PowerMock.expectNew(File.class, "directoryPath").andReturn(fileMock);
EasyMock.expect(fileMock.exists()).andReturn(false);
EasyMock.expect(fileMock.mkdirs()).andReturn(true);
PowerMock.replay(fileMock, File.class);
assertTrue(tested.createDirectoryStructure("directoryPath"));
PowerMock.verify(fileMock, File.class);
}
} FilefileMock = PowerMock.createMockAndExpectNew(File.class,“directoryPath”);