PowerMockito是什么？

PowerMockito是一个帮助我们快速写单测的工具，如果待测试方法中调用了其他方法或远程接口（如RPC、数据库等等），但是我们又不想在单测执行过程中真正的调用，而是mock出一个数据来，那么就可以使用PowerMockito+Mockito来实现了。

为什么有Mockito了还要使用PowerMockito？

Mockito也可以在单测中mock数据，那么为什么还需要使用PowerMockito呢？
因为PowerMockito的功能更加强大，可以实现Mockito不支持的功能如Mockito无法mock静态方法，对象创建等。

如何引入

     <dependency><groupId>org.mockito</groupId><artifactId>mockito-core</artifactId><version>3.11.2</version><scope>test</scope></dependency><dependency><groupId>org.mockito</groupId><artifactId>mockito-all</artifactId></dependency><dependency><groupId>org.powermock</groupId><artifactId>powermock-api-mockito2</artifactId><version>${powermock.version}</version><scope>test</scope></dependency>

注意事项

@PrepareForTest注解会影响jacoo统计覆盖率

比如编写PlusUtils.java的单测的时候，如果在单测类上使用注解：

@PrepareForTest({A.class})
@Test
public class ATest{}

那么A.class这个类的单测覆盖率会统计不到，即使对某个方法单测之前调用了类似：

PowerMockito.when(A.class,"methodName").thenCallRealMethod()

也是没用的

所以如果想提高某个类的单测覆盖率，千万不要将这个类放到@PrepareForTest注解中。

mockStatic报错

在调用mockStatic的时候可能会报错，如

java.lang.ExceptionInInitializerErrorat sun.reflect.GeneratedSerializationConstructorAccessor4.newInstance(Unknown Source)at java.lang.reflect.Constructor.newInstance(Constructor.java:423)at org.objenesis.instantiator.sun.SunReflectionFactoryInstantiator.newInstance(SunReflectionFactoryInstantiator.java:48)at org.objenesis.ObjenesisBase.newInstance(ObjenesisBase.java:73)at org.mockito.internal.creation.instance.ObjenesisInstantiator.newInstance(ObjenesisInstantiator.java:22)at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMock(SubclassByteBuddyMockMaker.java:48)at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createMock(ByteBuddyMockMaker.java:43)at org.powermock.api.mockito.mockmaker.PowerMockMaker.createMock(PowerMockMaker.java:41)at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:53)at org.mockito.internal.MockitoCore.mock(MockitoCore.java:84)at org.mockito.Mockito.mock(Mockito.java:1954)at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.createMethodInvocationControl(DefaultMockCreator.java:108)at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.doCreateMock(DefaultMockCreator.java:61)at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.createMock(DefaultMockCreator.java:53)at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.mock(DefaultMockCreator.java:40)at org.powermock.api.mockito.PowerMockito.mockStatic(PowerMockito.java:62)at com.dp.search.cloudsearch.utils.PlusUtilTest.testGetPlusByAppkey(PlusUtilTest.java:27)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:68)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:326)at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:89)at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:310)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:131)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.access$100(PowerMockJUnit47RunnerDelegateImpl.java:59)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner$TestExecutorStatement.evaluate(PowerMockJUnit47RunnerDelegateImpl.java:147)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.evaluateStatement(PowerMockJUnit47RunnerDelegateImpl.java:107)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:298)at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:218)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:160)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:134)at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:136)at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:117)at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:57)at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)at org.junit.runner.JUnitCore.run(JUnitCore.java:137)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: java.lang.IllegalArgumentException: Item may not be nullat org.apache.http.util.Args.notNull(Args.java:54)at org.apache.http.config.RegistryBuilder.register(RegistryBuilder.java:56)at com.dp.search.cloudsearch.utils.HttpClientUtil.<clinit>(HttpClientUtil.java:79)... 48 more

这种大概率是因为mock的静态类，在构造函数或者静态变量或者静态代码块执行了某些操作，导致mock失败

解决方式：单测类增加SuppressStaticInitializationFor注解，如：

@RunWith(PowerMockRunner.class)
@PrepareForTest({S3Utils.class, LionUtils.class, Lion.class, OPSUtils.class, RegionManagerLoader.class})
@SuppressStaticInitializationFor({"com.dp.search.cloudsearch.utils.HttpClientUtil","com.dp.search.cloudsearch.utils.S3Utils", "com.dp.search.cloudsearch.utils.LionUtils"})
public class AppServiceImplTest {}

SuppressStaticInitializationFor注解的意思是在mock这个静态类的时候不进行静态初始化。

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