Mockito cannot mock final classes error

[khahani]

To fix the below error which occurs when running unit tests that have a dependency with the UserManager class, we need to update Mockito to a version higher than 5.0.0 because mocking final classes feature is enabled by default. In my case updating Mockito to version 5.3.1 fixed the issue.

Solution:
testImplementation 'org.mockito:mockito-core:5.3.1'

Problem:

Mockito cannot mock this class: class com.example.android.dagger.user.UserManager.
Can not mock final classes with the following settings :
 - explicit serialization (e.g. withSettings().serializable())
 - extra interfaces (e.g. withSettings().extraInterfaces(...))

You are seeing this disclaimer because Mockito is configured to create inlined mocks.
You can learn about inline mocks and their limitations under item #39 of the Mockito class javadoc.

Underlying exception : org.mockito.exceptions.base.MockitoException: Could not modify all classes [class java.lang.Object, class com.example.android.dagger.user.UserManager]
org.mockito.exceptions.base.MockitoException: 
Mockito cannot mock this class: class com.example.android.dagger.user.UserManager.
Can not mock final classes with the following settings :
 - explicit serialization (e.g. withSettings().serializable())
 - extra interfaces (e.g. withSettings().extraInterfaces(...))

You are seeing this disclaimer because Mockito is configured to create inlined mocks.
You can learn about inline mocks and their limitations under item #39 of the Mockito class javadoc.

Underlying exception : org.mockito.exceptions.base.MockitoException: Could not modify all classes [class java.lang.Object, class com.example.android.dagger.user.UserManager]
	at app//com.example.android.dagger.registration.RegistrationViewModelTest.setup(RegistrationViewModelTest.kt:32)
	at java.base@17.0.6/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base@17.0.6/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base@17.0.6/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base@17.0.6/java.lang.reflect.Method.invoke(Unknown Source)
	at app//org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at app//org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at app//org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at app//org.junit.internal.runners.statements.RunBefores.invokeMethod(RunBefores.java:33)
	at app//org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
	at app//org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at app//org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at app//org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at app//org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at app//org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at app//org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at app//org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at app//org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at app//org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at app//org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at app//org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at app//org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.runTestClass(JUnitTestClassExecutor.java:110)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:58)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:38)
	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:62)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
	at java.base@17.0.6/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base@17.0.6/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at java.base@17.0.6/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.base@17.0.6/java.lang.reflect.Method.invoke(Unknown Source)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at jdk.proxy1/jdk.proxy1.$Proxy2.processTestClass(Unknown Source)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:176)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:133)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:71)
	at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
	at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: org.mockito.exceptions.base.MockitoException: Could not modify all classes [class java.lang.Object, class com.example.android.dagger.user.UserManager]
	at app//net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:152)
	at app//net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:365)
	at app//net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:174)
	at app//net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:376)
	... 45 more
Caused by: java.lang.IllegalStateException: 
Byte Buddy could not instrument all classes within the mock's type hierarchy

This problem should never occur for javac-compiled classes. This problem has been observed for classes that are:
 - Compiled by older versions of scalac
 - Classes that are part of the Android distribution
	at org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.triggerRetransformation(InlineBytecodeGenerator.java:237)
	at org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.mockClass(InlineBytecodeGenerator.java:198)
	at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$1.call(TypeCachingBytecodeGenerator.java:46)
	at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$1.call(TypeCachingBytecodeGenerator.java:43)
	at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:152)
	at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:365)
	at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:174)
	at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:376)
	at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.mockClass(TypeCachingBytecodeGenerator.java:36)
	at org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker.createMockType(InlineByteBuddyMockMaker.java:252)
	at org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker.createMock(InlineByteBuddyMockMaker.java:231)
	at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:35)
	at org.mockito.internal.MockitoCore.mock(MockitoCore.java:69)
	at org.mockito.Mockito.mock(Mockito.java:1933)
	at org.mockito.Mockito.mock(Mockito.java:1844)
	... 45 more
Caused by: java.lang.IllegalArgumentException: Unsupported class file major version 61
	at net.bytebuddy.jar.asm.ClassReader.<init>(ClassReader.java:196)
	at net.bytebuddy.jar.asm.ClassReader.<init>(ClassReader.java:177)
	at net.bytebuddy.jar.asm.ClassReader.<init>(ClassReader.java:163)
	at net.bytebuddy.utility.OpenedClassReader.of(OpenedClassReader.java:86)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForInlining.create(TypeWriter.java:3824)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:2166)
	at net.bytebuddy.dynamic.scaffold.inline.RedefinitionDynamicTypeBuilder.make(RedefinitionDynamicTypeBuilder.java:224)
	at net.bytebuddy.dynamic.scaffold.inline.AbstractInliningDynamicTypeBuilder.make(AbstractInliningDynamicTypeBuilder.java:123)
	at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:3595)
	at org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.transform(InlineBytecodeGenerator.java:344)
	at java.instrument/java.lang.instrument.ClassFileTransformer.transform(Unknown Source)
	at java.instrument/sun.instrument.TransformerManager.transform(Unknown Source)
	at java.instrument/sun.instrument.InstrumentationImpl.transform(Unknown Source)
	at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
	at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses(Unknown Source)
	at org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator.triggerRetransformation(InlineBytecodeGenerator.java:233)
	... 59 more

[MahdiRahmani80]

thank you, it works for me:
I implementing the last version of Mokito:

testImplementation 'org.mockito:mockito-core:5.6.0'

[amazingvoice]

Thank you for posting this. Just an update:
I upgraded mockito to testImplementation 'org.mockito:mockito-core:5.12.0' and it worked.