Trying to mock static system class with PowerMock gives VerifyError

Question

I am trying to mock JOptionPane static methods, and am stuck at a Java.lang.VerifyError. All versions are current, since I just downloaded PowerMock for Mockito, and all their dependencies.

I cannot use the answer given for a previous question, to wrap the class and subclass the wrapper - this is all over our application. I've invested a fair amount of time in PowerMock at this point, and I don't want to start over with fest.

Is there a way to resolve this error? I've tried both "Mocking Static Methods" and "Mocking System Classes" in the instructions. I can't go any farther since all I've done is @RunWith(PowerMockRunner.class) and @PrepareForTest(My.class).

I found that I could reduce this to an issue with any reference to a class that extends JPanel. Here is a minimum test to create the issue (I've gotten the same exception with PrepareForTest on Boffo and on JPanel):

import javax.swing.JPanel;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
//@PrepareForTest(JPanel.class)
@PrepareForTest(TestCase.Boffo.class)
public class TestCase {

    @SuppressWarnings("serial")
    public static class Boffo extends JPanel {}

    @Test
    public void test() throws Exception {
        new Boffo();
    }
}

Here is the exception I get when I try to run the test:

java.lang.VerifyError: (class: javax/swing/plaf/metal/MetalLookAndFeel, method: getLayoutStyle signature: ()Ljavax/swing/LayoutStyle;) Wrong return type in function
    at javax.swing.UIManager.setLookAndFeel(Unknown Source)
    at javax.swing.UIManager.initializeDefaultLAF(Unknown Source)
    at javax.swing.UIManager.initialize(Unknown Source)
    at javax.swing.UIManager.maybeInitialize(Unknown Source)
    at javax.swing.UIManager.getUI(Unknown Source)
    at javax.swing.JPanel.updateUI(Unknown Source)
    at javax.swing.JPanel.<init>(Unknown Source)
    at javax.swing.JPanel.<init>(Unknown Source)
    at javax.swing.JPanel.<init>(Unknown Source)
    at com.package.TestCase$Boffo.<init>(TestCase.java:17)
    at com.package.TestCase.test(TestCase.java:21)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:66)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:312)
    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:296)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:284)
    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:209)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:148)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:122)
    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:120)
    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.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:42)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
    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)

Answer 1

Here's a neat workaround/solution that a colleague of mine discovered today: Just add the annotation @PowerMockIgnore("javax.swing.*") to the test class and PowerMock will defer the loading of the problematic classes to the system classloader.

edit: Just re-read the question and since you're trying to mock JOptionPane itself I'm not sure this will help, but maybe you can play around with the exclusions pattern.

Answer 2

I have no idea actually why it throws VerifyError, but you can overcome it by setting a fake LookAndFill in advance before instantiating the class.

public static class FakeLookAndFill extends BasicLookAndFeel {
    @Override
    public String getName() {
        return "FakeLookAndFill";
    }

    @Override
    public String getID() {
        return "FakeLookAndFill";
    }

    @Override
    public String getDescription() {
        return "FakeLookAndFill";
    }

    @Override
    public boolean isNativeLookAndFeel() {
        return false;
    }

    @Override
    public boolean isSupportedLookAndFeel() {
        //note it returns true
        return true;
    }
}

@Before
public void setUp() throws Exception {
    UIManager.setLookAndFeel(new FakeLookAndFill());
}