how to mock private static method in java with PowerMockito which invoked by static Initializer?

Question

i'm trying to mock a static method like below,but i'm blocked by static initializer. see code below:

public class StaticInitializerService {

static{
    init();
}

private static void init(){
    throw new UnsupportedOperationException();
}

private static String getString(){
    throw new UnsupportedOperationException();
}

public static String method(){
    return getString();
}
}

here is my test case:

@PrepareForTest(StaticInitializerService.class)
public class StaticInitializerServiceTest   extends PowerMockTestCase{
@ObjectFactory
public ITestObjectFactory getObjectFactory() {
    return new PowerMockObjectFactory();
}

@Test
public void method() {
  PowerMockito.mockStatic(StaticInitializerService.class);
}
}

i'm try to use mockstatic and spy ,it all raise the following exception:

java.lang.ExceptionInInitializerError
at sun.reflect.GeneratedSerializationConstructorAccessor4.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.objenesis.instantiator.sun.SunReflectionFactoryInstantiator.newInstance(SunReflectionFactoryInstantiator.java:45)
at org.objenesis.ObjenesisBase.newInstance(ObjenesisBase.java:73)
at org.mockito.internal.creation.instance.ObjenesisInstantiator.newInstance(ObjenesisInstantiator.java:14)
at org.powermock.api.mockito.repackaged.ClassImposterizer.createProxy(ClassImposterizer.java:143)
at org.powermock.api.mockito.repackaged.ClassImposterizer.imposterise(ClassImposterizer.java:58)
at org.powermock.api.mockito.internal.mockcreation.MockCreator.createMethodInvocationControl(MockCreator.java:111)
at org.powermock.api.mockito.internal.mockcreation.MockCreator.mock(MockCreator.java:59)
at org.powermock.api.mockito.PowerMockito.spy(PowerMockito.java:234)
at com.zghome.mvndemo.TestNGDemo.powermock.service.testng.StaticInitializerServiceTest.method(StaticInitializerServiceTest.java:22)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:639)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:816)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1124)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:108)
at org.testng.TestRunner.privateRun(TestRunner.java:774)
at org.testng.TestRunner.run(TestRunner.java:624)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:359)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:354)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:312)
at org.testng.SuiteRunner.run(SuiteRunner.java:261)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1215)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1140)
at org.testng.TestNG.run(TestNG.java:1048)
at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:126)
at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:152)
at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:57)
Caused by: java.lang.UnsupportedOperationException
at     com.zghome.mvndemo.TestNGDemo.powermock.service.StaticInitializerService.init(St aticInitializerService.java:10)
at com.zghome.mvndemo.TestNGDemo.powermock.service.StaticInitializerService.  <clinit>(StaticInitializerService.java:6)
... 35 more

I suppose that i can't mock this class like this, but i don't know how to mock this. Any ideas how can i fix it?

Answer 1

Please add the below line to avoid the mentioned exception

@SuppressStaticInitializationFor("packageName.StaticInitializerService")

Then rest of the mocking will be similar to static void method mocking and PowerMockito.doThrow() method to thow the exception.here is the sample code which is not throwing any exception for your class

    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.powermock.api.mockito.PowerMockito;
    import org.powermock.core.classloader.annotations.PrepareForTest;
    import org.powermock.core.classloader.annotations.SuppressStaticInitializationFor;
    import org.powermock.modules.junit4.PowerMockRunner;
    @RunWith(PowerMockRunner.class)
    @PrepareForTest(StaticInitializerService.class)
    @SuppressStaticInitializationFor("PackageName.StaticInitializerService")
    public class StaticInitializerServiceTest {
    @Test 
    public void method() {
    PowerMockito.mockStatic(StaticInitializerService.class);
    }   
  }