Mockito - Mockito cannot mock this class - IllegalArgumentException: Could not create type

Question

I was trying to use a Mock class in a test of mine and getting this error:

org.mockito.exceptions.base.MockitoException: 
Mockito cannot mock this class: class com.example.Car.

Mockito can only mock non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.


Java               : 1.8
JVM vendor name    : Oracle Corporation
JVM vendor version : 25.161-b12
JVM name           : Java HotSpot(TM) Client VM
JVM version        : 1.8.0_161-b12
JVM info           : mixed mode, sharing
OS name            : Windows 10
OS version         : 10.0


Underlying exception : java.lang.IllegalArgumentException: Could not create type

at org.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:43)
at org.junit.rules.ExpectedException$ExpectedExceptionStatement.evaluate(ExpectedException.java:239)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
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.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:74)
at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:80)
at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.IllegalArgumentException: Could not create type
at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:139)
at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:344)
at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:159)
at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:353)
at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.mockClass(TypeCachingBytecodeGenerator.java:32)
at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMockType(SubclassByteBuddyMockMaker.java:71)
at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMock(SubclassByteBuddyMockMaker.java:42)
at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createMock(ByteBuddyMockMaker.java:25)
at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:35)
at org.mockito.internal.MockitoCore.mock(MockitoCore.java:62)
at org.mockito.Mockito.mock(Mockito.java:1908)
at org.mockito.internal.configuration.MockAnnotationProcessor.processAnnotationForMock(MockAnnotationProcessor.java:44)
at org.mockito.internal.configuration.MockAnnotationProcessor.process(MockAnnotationProcessor.java:19)
at org.mockito.internal.configuration.MockAnnotationProcessor.process(MockAnnotationProcessor.java:16)
at org.mockito.internal.configuration.IndependentAnnotationEngine.createMockFor(IndependentAnnotationEngine.java:38)
at org.mockito.internal.configuration.IndependentAnnotationEngine.process(IndependentAnnotationEngine.java:62)
at org.mockito.internal.configuration.InjectingAnnotationEngine.processIndependentAnnotations(InjectingAnnotationEngine.java:49)
at org.mockito.internal.configuration.InjectingAnnotationEngine.process(InjectingAnnotationEngine.java:41)
at org.mockito.MockitoAnnotations.initMocks(MockitoAnnotations.java:69)
... 21 more
Caused by: java.lang.NoSuchMethodError: net.bytebuddy.dynamic.loading.MultipleParentClassLoader$Builder.appendMostSpecific(Ljava/util/Collection;)Lnet/bytebuddy/dynamic/loading/MultipleParentClassLoader$Builder;
at org.mockito.internal.creation.bytebuddy.SubclassBytecodeGenerator.mockClass(SubclassBytecodeGenerator.java:83)
at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$1.call(TypeCachingBytecodeGenerator.java:37)
at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$1.call(TypeCachingBytecodeGenerator.java:34)
at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:137)
... 39 more

---

In the pom:

     <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>2.28.2</version>
        <scope>test</scope>
    </dependency>

(Also tried version 3.0.0 )

class Car :

public class Car{

  // Some properties. Non of them is final / static.

 // constructor
}

Test class:

@RunWith(MockitoJUnitRunner.class)
public class ParkinglotTest{

@Mock
private Car car;

private Parkinglog parkinglot;

@Before
 public void setUp(){
    parkinglot = new Parkinglot(car);
}


....

Answer 1

In my case, it was caused because it was referring to another version of byte-buddy which was actually not compatible with the mockito library.

This additional version of byte-buddy, coming from hibernate-core (version 5.3.7) which was also present in my classpath.

Initially, I was using mockito-core library version-3.3.3 which actually required byte-buddy 1.10.5.

So, I downgraded the mockito-core library to 2.21.0 version which uses byte-buddy version 1.8.15.

And it started working fine for me.

An additional solution for me was to update to a newer version of hibernate (version>=5.4.11.Final) which includes byte-buddy version compatible with the mockito library.

But that could have a larger impact on the project so I went for the first solution like follows depending on which library you are using :

    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-junit-jupiter</artifactId>
        <version>2.21.0</version>
        <scope>test</scope>
    </dependency>

OR

    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>2.21.0</version>
        <scope>test</scope>
    </dependency>

Also, this issue was being addressed here: https://github.com/mockito/mockito/issues/1606 which helped me to find the solution for me.

Answer 2

It seems that this might be caused because it can't find bytebuddy installed, referring to:

Caused by: java.lang.NoSuchMethodError: net.bytebuddy.dynamic.loading.MultipleParentClassLoader$Builder.appendMostSpecific(Ljava/util/Collection;)Lnet/bytebuddy/dynamic/loading/MultipleParentClassLoader$Builder;

From what I can find online adding bytebuddy to your dependencies might fix this.

    <dependency>
      <groupId>net.bytebuddy</groupId>
      <artifactId>byte-buddy</artifactId>
      <version>XXX</version>
    </dependency>

Answer 3

I was able to fix the problem after downgrading the Mockito version:

<version>2.13.0</version>