Mockito with Robolectric: "ClassCastException occurred when creating the proxy"

Question

I've started hitting a strange ClassCastException in Mockito when using it with Robolectric. When I run the same tests not using Robolectric runner, everything goes fine, no exception is thrown.

Here is stack trace:

org.mockito.exceptions.base.MockitoException: 
ClassCastException occurred when creating the proxy.
You might experience classloading issues, disabling the Objenesis cache *might* help (see MockitoConfiguration)
    at com.compassrosetech.ccs.android.test.ObservableCacheDispatcherTest.setUp(ObservableCacheDispatcherTest.java:63)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
    at org.robolectric.RobolectricTestRunner$2.evaluate(RobolectricTestRunner.java:236)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.robolectric.RobolectricTestRunner$1.evaluate(RobolectricTestRunner.java:158)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:211)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:67)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: java.lang.ClassCastException: kotlin.Function0$$EnhancerByMockitoWithCGLIB$$c0163e7f cannot be cast to org.mockito.cglib.proxy.Factory
    at org.mockito.internal.creation.jmock.ClassImposterizer.createProxy(ClassImposterizer.java:128)
    at org.mockito.internal.creation.jmock.ClassImposterizer.imposterise(ClassImposterizer.java:63)
    at org.mockito.internal.creation.jmock.ClassImposterizer.imposterise(ClassImposterizer.java:56)
    at org.mockito.internal.creation.CglibMockMaker.createMock(CglibMockMaker.java:23)
    at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:26)
    at org.mockito.internal.MockitoCore.mock(MockitoCore.java:51)
    at org.mockito.Mockito.mock(Mockito.java:1243)
    at org.mockito.internal.configuration.MockAnnotationProcessor.process(MockAnnotationProcessor.java:30)
    at org.mockito.internal.configuration.MockAnnotationProcessor.process(MockAnnotationProcessor.java:16)
    at org.mockito.internal.configuration.DefaultAnnotationEngine.createMockFor(DefaultAnnotationEngine.java:43)
    at org.mockito.internal.configuration.DefaultAnnotationEngine.process(DefaultAnnotationEngine.java:66)
    at org.mockito.internal.configuration.InjectingAnnotationEngine.processIndependentAnnotations(InjectingAnnotationEngine.java:71)
    at org.mockito.internal.configuration.InjectingAnnotationEngine.process(InjectingAnnotationEngine.java:55)
    at org.mockito.MockitoAnnotations.initMocks(MockitoAnnotations.java:108)
    ... 29 more

The code I'm using is as follows:

@RunWith(ApplicationTestRunner.class)
public class ObservableCacheDispatcherTest {

    @Mock
    private IDataMapper mockDataMapper;

    @Mock
    private ICache mockCache;

    @Mock
    private Function0<Object> mockLoader;

    private ObservableCacheDispatcher cacheDispatcher;


    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this); // <-- exception happens when executing this statement
        cacheDispatcher = new ObservableCacheDispatcher(mockCache, mockDataMapper);
    }

    ...
}

This is how Robolectric runner looks like:

public class ApplicationTestRunner extends RobolectricTestRunner {

    //Maximun SDK Robolectric will compile (issues with SDK > 18)
    private static final int MAX_SDK_SUPPORTED_BY_ROBOLECTRIC = 18;

    private static final String ANDROID_MANIFEST_PATH = "../app/src/main/AndroidManifest.xml";
    private static final String ANDROID_MANIFEST_RES_PATH = "../app/src/main/res";

    /**
     * Call this constructor to specify the location of resources and AndroidManifest.xml.
     *
     * @throws org.junit.runners.model.InitializationError
     */
    public ApplicationTestRunner(Class<?> testClass) throws InitializationError {
        super(testClass);
    }

    @Override protected AndroidManifest getAppManifest(Config config) {
        return new AndroidManifest(Fs.fileFromPath(ANDROID_MANIFEST_PATH),
                Fs.fileFromPath(ANDROID_MANIFEST_RES_PATH)) {
            @Override
            public int getTargetSdkVersion() {
                return MAX_SDK_SUPPORTED_BY_ROBOLECTRIC;
            }
        };
    }
}

What should I fix to get rid of this exception?

Answer 1

As suggested

'disabling the Objenesis cache might help'

You can create override MockitoConfiguration.
To do so

• Create a package named org.mockito.configuration under your src/test/java
• Write the MockitoConfiguration class

Class File

package org.mockito.configuration;

public class MockitoConfiguration extends DefaultMockitoConfiguration {

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

Try to build your code again.

Answer 2

I know question is bit old, but it may help someone looking for the answer.

Adding

@PowerMockIgnore({ "org.mockito.*"})

After

@RunWith(ApplicationTestRunner.class)

Should solve the issue.