一、為什么要使用Mock工具
在做單元測試的時候,我們會發現我們要測試的方法會引用很多外部依賴的對象,比如:(發送郵件,網絡通訊,遠程服務, 文件系統等等)。 而我們沒法控制這些外部依賴的對象,為了解決這個問題,我們就需要用到Mock工具來模擬這些外部依賴的對象,來完成單元測試。
二、為什么要使用PowerMock
現如今比較流行的Mock工具如EasyMock 、Mockito等都有一個共同的缺點:不能mock靜態、final、私有方法等。而PowerMock能夠完美的彌補以上三個Mock工具的不足。
三、PowerMock簡介
PowerMock是一個擴展了其它如EasyMock等mock框架的、功能更加強大的框架。PowerMock使用一個自定義類加載器和字節碼操作來模擬靜態方法,構造函數,final類和方法,私有方法,去除靜態初始化器等等。通過使用自定義的類加載器,簡化采用的IDE或持續集成服務器不需要做任何改變。熟悉PowerMock支持的mock框架的開發人員會發現PowerMock很容易使用,因為對於靜態方法和構造器來說,整個的期望API是一樣的。PowerMock旨在用少量的方法和注解擴展現有的API來實現額外的功能。目前PowerMock支持EasyMock和Mockito。
四、PowerMock入門
PowerMock有兩個重要的注解:
–@RunWith(PowerMockRunner.class)
–@PrepareForTest( { YourClassWithEgStaticMethod.class })
如果你的測試用例里沒有使用注解@PrepareForTest,那么可以不用加注解@RunWith(PowerMockRunner.class),反之亦然。當你需要使用PowerMock強大功能(Mock靜態、final、私有方法等)的時候,就需要加注解@PrepareForTest。
五、PowerMock基本用法
(1) 普通Mock: Mock參數傳遞的對象
測試目標代碼:
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public boolean callArgumentInstance(File file) { |
2 |
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return file.exists(); |
4 |
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} |
測試用例代碼:
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@Test |
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public void testCallArgumentInstance() { |
03 |
|
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File file = PowerMockito.mock(File. class ); |
05 |
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ClassUnderTest underTest = new ClassUnderTest(); |
07 |
|
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PowerMockito.when(file.exists()).thenReturn( true ); |
09 |
|
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Assert.assertTrue(underTest.callArgumentInstance(file)); |
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} |
說明:普通Mock不需要加@RunWith和@PrepareForTest注解。
(2) Mock方法內部new出來的對象
測試目標代碼:
01 |
public class ClassUnderTest { |
02 |
03 |
public boolean callInternalInstance(String path) { |
04 |
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File file = new File(path); |
06 |
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return file.exists(); |
08 |
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} |
10 |
} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
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public class TestClassUnderTest { |
03 |
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@Test |
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@PrepareForTest (ClassUnderTest. class ) |
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public void testCallInternalInstance() throws Exception { |
07 |
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File file = PowerMockito.mock(File. class ); |
09 |
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ClassUnderTest underTest = new ClassUnderTest(); |
11 |
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PowerMockito.whenNew(File. class ).withArguments( "bbb" ).thenReturn(file); |
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|
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PowerMockito.when(file.exists()).thenReturn( true ); |
15 |
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Assert.assertTrue(underTest.callInternalInstance( "bbb" )); |
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} |
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} |
說明:當使用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。
(3) Mock普通對象的final方法
測試目標代碼:
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public class ClassUnderTest { |
2 |
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public boolean callFinalMethod(ClassDependency refer) { |
4 |
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return refer.isAlive(); |
6 |
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} |
8 |
} |
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public class ClassDependency { |
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|
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public final boolean isAlive() { |
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// do something |
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return false ; |
08 |
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} |
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} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
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public class TestClassUnderTest { |
03 |
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@Test |
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@PrepareForTest (ClassDependency. class ) |
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public void testCallFinalMethod() { |
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ClassDependency depencency = PowerMockito.mock(ClassDependency. class ); |
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|
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ClassUnderTest underTest = new ClassUnderTest(); |
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|
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PowerMockito.when(depencency.isAlive()).thenReturn( true ); |
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|
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Assert.assertTrue(underTest.callFinalMethod(depencency)); |
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|
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} |
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} |
說明: 當需要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。
(4) Mock普通類的靜態方法
測試目標代碼:
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public class ClassUnderTest { |
2 |
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public boolean callStaticMethod() { |
4 |
|
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return ClassDependency.isExist(); |
6 |
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} |
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} |
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public class ClassDependency { |
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|
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public static boolean isExist() { |
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// do something |
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return false ; |
08 |
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} |
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} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
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public class TestClassUnderTest { |
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@Test |
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@PrepareForTest (ClassDependency. class ) |
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public void testCallStaticMethod() { |
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|
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ClassUnderTest underTest = new ClassUnderTest(); |
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|
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PowerMockito.mockStatic(ClassDependency. class ); |
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PowerMockito.when(ClassDependency.isExist()).thenReturn( true ); |
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|
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Assert.assertTrue(underTest.callStaticMethod()); |
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|
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} |
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} |
說明:當需要mock靜態方法的時候,必須加注解@PrepareForTest和@RunWith。注解@PrepareForTest里寫的類是靜態方法所在的類。
(5) Mock 私有方法
測試目標代碼:
01 |
public class ClassUnderTest { |
02 |
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public boolean callPrivateMethod() { |
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return isExist(); |
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} |
08 |
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private boolean isExist() { |
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|
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return false ; |
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} |
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} |
測試用例代碼:
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@RunWith (PowerMockRunner. class ) |
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public class TestClassUnderTest { |
03 |
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@Test |
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@PrepareForTest (ClassUnderTest. class ) |
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public void testCallPrivateMethod() throws Exception { |
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ClassUnderTest underTest = PowerMockito.mock(ClassUnderTest. class ); |
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PowerMockito.when(underTest.callPrivateMethod()).thenCallRealMethod(); |
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PowerMockito.when(underTest, "isExist" ).thenReturn( true ); |
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|
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Assert.assertTrue(underTest.callPrivateMethod()); |
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|
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} |
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} |
說明:和Mock普通方法一樣,只是需要加注解@PrepareForTest(ClassUnderTest.class),注解里寫的類是私有方法所在的類。
(6) Mock系統類的靜態和final方法
測試目標代碼:
01 |
public class ClassUnderTest { |
02 |
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public boolean callSystemFinalMethod(String str) { |
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return str.isEmpty(); |
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} |
08 |
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public String callSystemStaticMethod(String str) { |
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|
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return System.getProperty(str); |
12 |
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} |
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} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
02 |
public class TestClassUnderTest { |
03 |
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@Test |
05 |
@PrepareForTest (ClassUnderTest. class ) |
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public void testCallSystemStaticMethod() { |
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ClassUnderTest underTest = new ClassUnderTest(); |
09 |
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PowerMockito.mockStatic(System. class ); |
11 |
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PowerMockito.when(System.getProperty( "aaa" )).thenReturn( "bbb" ); |
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|
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Assert.assertEquals( "bbb" , underTest.callJDKStaticMethod( "aaa" )); |
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} |
17 |
} |
說明:和Mock普通對象的靜態方法、final方法一樣,只不過注解@PrepareForTest里寫的類不一樣 ,注解里寫的類是需要調用系統方法所在的類。
六 、無所不能的PowerMock
(1) 驗證靜態方法:
PowerMockito.verifyStatic();
Static.firstStaticMethod(param);
(2) 擴展驗證:
PowerMockito.verifyStatic(Mockito.times(2)); // 被調用2次 Static.thirdStaticMethod(Mockito.anyInt()); // 以任何整數值被調用
(3) 更多的Mock方法
http://code.google.com/p/powermock/wiki/MockitoUsage13
七、PowerMock簡單實現原理
• 當某個測試方法被注解@PrepareForTest標注以后,在運行測試用例時,會創建一個新的org.powermock.core.classloader.MockClassLoader實例,然后加載該測試用例使用到的類(系統類除外)。
• PowerMock會根據你的mock要求,去修改寫在注解@PrepareForTest里的class文件(當前測試類會自動加入注解中),以滿足特殊的mock需求。例如:去除final方法的final標識,在靜態方法的最前面加入自己的虛擬實現等。
• 如果需要mock的是系統類的final方法和靜態方法,PowerMock不會直接修改系統類的class文件,而是修改調用系統類的class文件,以滿足mock需求。
powmock的maven依賴:
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-mockito</artifactId>
<version>1.6.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-module-junit4</artifactId>
<version>1.6.1</version>
<scope>test</scope>
</dependency>
1 |
public boolean callArgumentInstance(File file) { |
2 |
3 |
return file.exists(); |
4 |
5 |
} |
測試用例代碼:
01 |
@Test |
02 |
public void testCallArgumentInstance() { |
03 |
|
04 |
File file = PowerMockito.mock(File. class ); |
05 |
06 |
ClassUnderTest underTest = new ClassUnderTest(); |
07 |
|
08 |
PowerMockito.when(file.exists()).thenReturn( true ); |
09 |
|
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Assert.assertTrue(underTest.callArgumentInstance(file)); |
11 |
} |
說明:普通Mock不需要加@RunWith和@PrepareForTest注解。
(2) Mock方法內部new出來的對象
測試目標代碼:
01 |
public class ClassUnderTest { |
02 |
03 |
public boolean callInternalInstance(String path) { |
04 |
05 |
File file = new File(path); |
06 |
07 |
return file.exists(); |
08 |
09 |
} |
10 |
} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
02 |
public class TestClassUnderTest { |
03 |
04 |
@Test |
05 |
@PrepareForTest (ClassUnderTest. class ) |
06 |
public void testCallInternalInstance() throws Exception { |
07 |
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File file = PowerMockito.mock(File. class ); |
09 |
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ClassUnderTest underTest = new ClassUnderTest(); |
11 |
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PowerMockito.whenNew(File. class ).withArguments( "bbb" ).thenReturn(file); |
13 |
|
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PowerMockito.when(file.exists()).thenReturn( true ); |
15 |
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Assert.assertTrue(underTest.callInternalInstance( "bbb" )); |
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} |
18 |
} |
說明:當使用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。
(3) Mock普通對象的final方法
測試目標代碼:
1 |
public class ClassUnderTest { |
2 |
3 |
public boolean callFinalMethod(ClassDependency refer) { |
4 |
5 |
return refer.isAlive(); |
6 |
7 |
} |
8 |
} |
01 |
public class ClassDependency { |
02 |
|
03 |
public final boolean isAlive() { |
04 |
05 |
// do something |
06 |
07 |
return false ; |
08 |
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} |
10 |
} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
02 |
public class TestClassUnderTest { |
03 |
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@Test |
05 |
@PrepareForTest (ClassDependency. class ) |
06 |
public void testCallFinalMethod() { |
07 |
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ClassDependency depencency = PowerMockito.mock(ClassDependency. class ); |
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|
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ClassUnderTest underTest = new ClassUnderTest(); |
11 |
|
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PowerMockito.when(depencency.isAlive()).thenReturn( true ); |
13 |
|
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Assert.assertTrue(underTest.callFinalMethod(depencency)); |
15 |
|
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} |
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} |
說明: 當需要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。
(4) Mock普通類的靜態方法
測試目標代碼:
1 |
public class ClassUnderTest { |
2 |
3 |
public boolean callStaticMethod() { |
4 |
|
5 |
return ClassDependency.isExist(); |
6 |
7 |
} |
8 |
} |
01 |
public class ClassDependency { |
02 |
|
03 |
public static boolean isExist() { |
04 |
05 |
// do something |
06 |
07 |
return false ; |
08 |
09 |
} |
10 |
} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
02 |
public class TestClassUnderTest { |
03 |
04 |
@Test |
05 |
@PrepareForTest (ClassDependency. class ) |
06 |
public void testCallStaticMethod() { |
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|
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ClassUnderTest underTest = new ClassUnderTest(); |
09 |
|
10 |
PowerMockito.mockStatic(ClassDependency. class ); |
11 |
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PowerMockito.when(ClassDependency.isExist()).thenReturn( true ); |
13 |
|
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Assert.assertTrue(underTest.callStaticMethod()); |
15 |
|
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} |
17 |
} |
說明:當需要mock靜態方法的時候,必須加注解@PrepareForTest和@RunWith。注解@PrepareForTest里寫的類是靜態方法所在的類。
(5) Mock 私有方法
測試目標代碼:
01 |
public class ClassUnderTest { |
02 |
03 |
public boolean callPrivateMethod() { |
04 |
05 |
return isExist(); |
06 |
07 |
} |
08 |
09 |
private boolean isExist() { |
10 |
|
11 |
return false ; |
12 |
13 |
} |
14 |
} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
02 |
public class TestClassUnderTest { |
03 |
04 |
@Test |
05 |
@PrepareForTest (ClassUnderTest. class ) |
06 |
public void testCallPrivateMethod() throws Exception { |
07 |
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ClassUnderTest underTest = PowerMockito.mock(ClassUnderTest. class ); |
09 |
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PowerMockito.when(underTest.callPrivateMethod()).thenCallRealMethod(); |
11 |
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PowerMockito.when(underTest, "isExist" ).thenReturn( true ); |
13 |
|
14 |
Assert.assertTrue(underTest.callPrivateMethod()); |
15 |
|
16 |
} |
17 |
} |
說明:和Mock普通方法一樣,只是需要加注解@PrepareForTest(ClassUnderTest.class),注解里寫的類是私有方法所在的類。
(6) Mock系統類的靜態和final方法
測試目標代碼:
01 |
public class ClassUnderTest { |
02 |
03 |
public boolean callSystemFinalMethod(String str) { |
04 |
05 |
return str.isEmpty(); |
06 |
07 |
} |
08 |
09 |
public String callSystemStaticMethod(String str) { |
10 |
|
11 |
return System.getProperty(str); |
12 |
13 |
} |
14 |
} |
測試用例代碼:
01 |
@RunWith (PowerMockRunner. class ) |
02 |
public class TestClassUnderTest { |
03 |
04 |
@Test |
05 |
@PrepareForTest (ClassUnderTest. class ) |
06 |
public void testCallSystemStaticMethod() { |
07 |
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ClassUnderTest underTest = new ClassUnderTest(); |
09 |
10 |
PowerMockito.mockStatic(System. class ); |
11 |
12 |
PowerMockito.when(System.getProperty( "aaa" )).thenReturn( "bbb" ); |
13 |
|
14 |
Assert.assertEquals( "bbb" , underTest.callJDKStaticMethod( "aaa" )); |
15 |
16 |
} |
17 |
} |
說明:和Mock普通對象的靜態方法、final方法一樣,只不過注解@PrepareForTest里寫的類不一樣 ,注解里寫的類是需要調用系統方法所在的類。
六 、無所不能的PowerMock
(1) 驗證靜態方法:
PowerMockito.verifyStatic();
Static.firstStaticMethod(param);
(2) 擴展驗證:
PowerMockito.verifyStatic(Mockito.times(2)); // 被調用2次 Static.thirdStaticMethod(Mockito.anyInt()); // 以任何整數值被調用
(3) 更多的Mock方法
http://code.google.com/p/powermock/wiki/MockitoUsage13
七、PowerMock簡單實現原理
• 當某個測試方法被注解@PrepareForTest標注以后,在運行測試用例時,會創建一個新的org.powermock.core.classloader.MockClassLoader實例,然后加載該測試用例使用到的類(系統類除外)。
• PowerMock會根據你的mock要求,去修改寫在注解@PrepareForTest里的class文件(當前測試類會自動加入注解中),以滿足特殊的mock需求。例如:去除final方法的final標識,在靜態方法的最前面加入自己的虛擬實現等。
• 如果需要mock的是系統類的final方法和靜態方法,PowerMock不會直接修改系統類的class文件,而是修改調用系統類的class文件,以滿足mock需求。