Got ExceptionInInitializerError when mocking constructor of a class with Powermock. How to fix it?

Question

Here is my case. I have a AbstractController class. It has a sub class Controller. In one of AbstractController's methods a new ApplicationLock is instantiated. I'd like to mock ApplicationLock when writing ut for Controller. I wrote a test case like below.

@test
public void testMethod(){
    ApplicationLock mockLock=PowerMockito.mock(ApplicationLock.class);
    PowerMockito.when(mockLock.tryObtain()).thenReturn(true);
    PowerMockito.whenNew(ApplicationLock.class).withArguments(argThat(new IsFile()),anyString()).thenReturn(mockLock);
}

I've added necessary annotations to the test class.

@RunWith(PowerMockRunner.class)

@PrepareForTest({AbstractController.class})

But I got the following error when running this test case. That is a static initializer in AbstractController.

Caused by: java.lang.NullPointerException at com.acompany.controller.common.AbstractController.(AbstractController.java:65)

private static final String DEFAULT_FOLDER = AbstractController.class.getProtectionDomain().getCodeSource()
            .getLocation().getPath();

Full stack trace is as below.

java.lang.ExceptionInInitializerError at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at javassist.runtime.Desc.getClassObject(Desc.java:44) at javassist.runtime.Desc.getClassType(Desc.java:153) at javassist.runtime.Desc.getType(Desc.java:123) at javassist.runtime.Desc.getType(Desc.java:79) at com.acompany.controller.portfolio.ControllerTest.testIncrementalFail(ControllerTest.java:195) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:66) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:307) at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:86) at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:94) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:294) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:112) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:73) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:282) at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:84) at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:49) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:207) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:146) at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:120) 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:118) at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:102) at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:53) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) Caused by: java.lang.NullPointerException at com.acompany.controller.common.AbstractController.(AbstractController.java:65) ... 35 more

Answer 1

You could use then:

 @SuppressStaticInitializationFor({AbstractController.class})

And then, in your test case, set manually all static fields that need to be initialized, including the DEFAULT_FOLDER:

Whitebox.setInternalState(Controller.class, "DEFAULT_FOLDER", "abcd");
Whitebox.setInternalState(Controller.class, "OTHER_FIELD", new Object());

The method Class<?>.getProtectionDomain() depends too much on class loader used, so you probably won't get it to work in JUnit/PowerMock, which use their own.