title: Mockito object is not an instance of declaring class
body: <p>I haven't touched Mockito for a while, and I have never used it extensively. But today in some new code I wanted to use best practices so I pulled out mockito-core 2.0.54-beta using the following Java version:</p>
  
  <pre><code>java version "1.8.0"
  Java(TM) SE Runtime Environment (build 1.8.0-b132)
  Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)
  </code></pre>
  
  <p>I needed an instance of this interface for testing:</p>
  
  <p><a href="https://bitbucket.org/globalmentor/rincl/src/bf0e8875a1bae16247dd904e0b8bc067c9f8abc9/src/main/java/io/rincl/ResourceI18nConcern.java" rel="noreferrer">https://bitbucket.org/globalmentor/rincl/src/bf0e8875a1bae16247dd904e0b8bc067c9f8abc9/src/main/java/io/rincl/ResourceI18nConcern.java</a></p>
  
  <pre><code>public interface ResourceI18nConcern extends Concern {
  
      public Locale getLocale(@Nonnull Locale.Category category);
  
      public void setLocale(@Nonnull Locale.Category category, @Nonnull Locale locale);
  
      public default void setLocale(@Nonnull Locale locale) {...}
  
      public Resources getResources(@Nonnull final Class&lt;?&gt; contextClass) throws ResourceConfigurationException;
  
  }
  </code></pre>
  
  <p>That interface extends this one (just an empty marker interface):</p>
  
  <p><a href="https://bitbucket.org/globalmentor/csar/src/125b837e9936ddb8d6340fa99b6b5da872d1e6e5/src/main/java/io/csar/Concern.java" rel="noreferrer">https://bitbucket.org/globalmentor/csar/src/125b837e9936ddb8d6340fa99b6b5da872d1e6e5/src/main/java/io/csar/Concern.java</a></p>
  
  <p>In my test I tried to do this simple thing:</p>
  
  <pre><code>final ResourceI18nConcern defaultConcern=mock(ResourceI18nConcern.class);
  </code></pre>
  
  <p>I get the following stack trace:</p>
  
  <pre><code>org.mockito.exceptions.base.MockitoException:
  Mockito cannot mock this class: interface io.rincl.ResourceI18nConcern
  
  Mockito can only mock visible &amp; non-final classes.
  If you're not sure why you're getting this error, please report to the mailing list.
  
  Underlying exception : java.lang.IllegalArgumentException: object is not an instance of declaring class
      at io.rincl.RinclTest.defaultConcernRinclGetLocaleIsConcernLocale(RinclTest.java:91)
      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:483)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
      at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
  Caused by: java.lang.IllegalArgumentException: object is not an instance of declaring class
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:483)
      at net.bytebuddy.description.type.TypeDescription$Generic$AnnotationReader$ForTypeArgument.resolve(TypeDescription.java:3875)
      at net.bytebuddy.description.type.TypeDescription$Generic$AnnotationReader$Delegator$Chained.resolve(TypeDescription.java:3501)
      at net.bytebuddy.description.type.TypeDescription$Generic$AnnotationReader$ForTypeArgument.resolve(TypeDescription.java:3834)
      at net.bytebuddy.description.type.TypeDescription$Generic$AnnotationReader$Delegator.asList(TypeDescription.java:3477)
      at net.bytebuddy.description.type.TypeDescription$Generic$OfWildcardType$ForLoadedType.getDeclaredAnnotations(TypeDescription.java:4771)
      at net.bytebuddy.description.type.TypeDescription$Generic$Visitor$TypeVariableErasing.onWildcard(TypeDescription.java:676)
      at net.bytebuddy.description.type.TypeDescription$Generic$Visitor$TypeVariableErasing.onWildcard(TypeDescription.java:659)
      at net.bytebuddy.description.type.TypeDescription$Generic$OfWildcardType.accept(TypeDescription.java:4679)
      at net.bytebuddy.description.type.TypeDescription$Generic$Visitor$TypeVariableErasing.onParameterizedType(TypeDescription.java:687)
      at net.bytebuddy.description.type.TypeDescription$Generic$Visitor$TypeVariableErasing.onParameterizedType(TypeDescription.java:659)
      at net.bytebuddy.description.type.TypeDescription$Generic$OfParameterizedType.accept(TypeDescription.java:5021)
      at net.bytebuddy.description.type.TypeDescription$Generic$LazyProjection.accept(TypeDescription.java:5794)
      at net.bytebuddy.description.method.ParameterDescription$TypeSubstituting.getType(ParameterDescription.java:866)
      at net.bytebuddy.description.method.ParameterList$AbstractBase.asTypeList(ParameterList.java:85)
      at net.bytebuddy.description.method.MethodDescription$AbstractBase.asTypeToken(MethodDescription.java:635)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$Default$Key$Harmonized.of(MethodGraph.java:862)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$Default$Key$Store.registerTopLevel(MethodGraph.java:1059)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$Default.doAnalyze(MethodGraph.java:569)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$Default.analyze(MethodGraph.java:529)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$Default.doAnalyze(MethodGraph.java:565)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$Default.compile(MethodGraph.java:502)
      at net.bytebuddy.dynamic.scaffold.MethodGraph$Compiler$AbstractBase.compile(MethodGraph.java:423)
      at net.bytebuddy.dynamic.scaffold.MethodRegistry$Default.prepare(MethodRegistry.java:489)
      at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:153)
      at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:2564)
      at org.mockito.internal.creation.bytebuddy.MockBytecodeGenerator.generateMockClass(MockBytecodeGenerator.java:60)
      at org.mockito.internal.creation.bytebuddy.CachingMockBytecodeGenerator$CachedBytecodeGenerator.generate(CachingMockBytecodeGenerator.java:72)
      at org.mockito.internal.creation.bytebuddy.CachingMockBytecodeGenerator$CachedBytecodeGenerator.getOrGenerateMockClass(CachingMockBytecodeGenerator.java:64)
      at org.mockito.internal.creation.bytebuddy.CachingMockBytecodeGenerator.get(CachingMockBytecodeGenerator.java:27)
      at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createProxyClass(ByteBuddyMockMaker.java:54)
      at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createMock(ByteBuddyMockMaker.java:27)
      at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:32)
      at org.mockito.internal.MockitoCore.mock(MockitoCore.java:54)
      at org.mockito.Mockito.mock(Mockito.java:1443)
      at org.mockito.Mockito.mock(Mockito.java:1356)
      ... 26 more
  </code></pre>
  
  <p>Am I doing something wrong? This seemed to me as if it should be straightforward.</p>
  
  <p>To reproduce this problem, clone <a href="https://bitbucket.org/globalmentor/rincl.git" rel="noreferrer">https://bitbucket.org/globalmentor/rincl.git</a> and check out commit 2f88d7c5e5ac17b6d316ed54c12cb7b447b7d6ac. Then try to run the following test:</p>
  
  <pre><code>import static org.junit.Assert.*;
  import static org.hamcrest.Matchers.*;
  import static org.mockito.Mockito.*;
  import java.util.Locale;
  import java.util.Locale.Category;
  import org.junit.*;
  
  public class RinclTest {
      @Test
      public void defaultConcernRinclGetLocaleIsConcernLocale() {
          final ResourceI18nConcern defaultConcern=mock(ResourceI18nConcern.class);
      }
  }
  </code></pre>