Getting Exception within JMockit Library when using with JUNIT5

Question

I'm trying to convert all of my JUNIT4 test cases to JUNIT5 test cases that were using Jmockit. When I managed to convert one of them and execute, I'm getting this error within JMockit Library that is a dependency for my application,

java.lang.NullPointerException
    at mockit.internal.startup.Startup.retransformClass(Startup.java:98)
    at mockit.internal.state.CachedClassfiles.getClassfile(CachedClassfiles.java:123)
    at mockit.internal.ClassFile.createReaderOrGetFromCache(ClassFile.java:92)
    at mockit.internal.classGeneration.ImplementationClass.generateClass(ImplementationClass.java:35)
    at mockit.internal.expectations.mocking.BaseTypeRedefinition.generateNewMockImplementationClassForInterface(BaseTypeRedefinition.java:163)
    at mockit.internal.expectations.mocking.BaseTypeRedefinition.createMockInterfaceImplementationDirectly(BaseTypeRedefinition.java:124)
    at mockit.internal.expectations.mocking.BaseTypeRedefinition.createMockedInterfaceImplementationAndInstanceFactory(BaseTypeRedefinition.java:84)
    at mockit.internal.expectations.mocking.BaseTypeRedefinition.redefineType(BaseTypeRedefinition.java:61)
    at mockit.internal.expectations.mocking.TypeRedefinition.redefineType(TypeRedefinition.java:28)
    at mockit.internal.expectations.mocking.FieldTypeRedefinitions.redefineFieldType(FieldTypeRedefinitions.java:78)
    at mockit.internal.expectations.mocking.FieldTypeRedefinitions.redefineFieldType(FieldTypeRedefinitions.java:65)
    at mockit.internal.expectations.mocking.FieldTypeRedefinitions.redefineFieldTypes(FieldTypeRedefinitions.java:53)
    at mockit.internal.expectations.mocking.FieldTypeRedefinitions.<init>(FieldTypeRedefinitions.java:33)
    at mockit.integration.TestRunnerDecorator.handleMockFieldsForWholeTestClass(TestRunnerDecorator.java:142)
    at mockit.integration.junit5.JMockitExtension.postProcessTestInstance(JMockitExtension.java:52)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.lambda$invokeTestInstancePostProcessors$5(ClassTestDescriptor.java:349)
    at org.junit.jupiter.engine.descriptor.JupiterTestDescriptor.executeAndMaskThrowable(JupiterTestDescriptor.java:215)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.lambda$invokeTestInstancePostProcessors$6(ClassTestDescriptor.java:349)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
    at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312)
    at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:743)
    at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:742)
    at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.invokeTestInstancePostProcessors(ClassTestDescriptor.java:348)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.instantiateAndPostProcessTestInstance(ClassTestDescriptor.java:270)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.lambda$testInstanceProvider$2(ClassTestDescriptor.java:259)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.lambda$testInstanceProvider$3(ClassTestDescriptor.java:263)
    at java.util.Optional.orElseGet(Optional.java:267)
    at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.lambda$testInstanceProvider$4(ClassTestDescriptor.java:262)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:82)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:59)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$0(NodeTestTask.java:83)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:72)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:83)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:69)
    at java.util.ArrayList.forEach(ArrayList.java:1257)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$4(NodeTestTask.java:112)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:72)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:98)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:74)
    at java.util.ArrayList.forEach(ArrayList.java:1257)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$4(NodeTestTask.java:112)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:72)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:98)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:74)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:170)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:154)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:90)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:69)
    at com.intellij.rt.execution.junit.IdeaTestRunner$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)

Please find sample code in here that can be used for debugging,

https://github.com/siva54/jmockit-junit5-stackoverflow/blob/master/test/java8testing/JUnit5Test.java

JMockit Version: 1.47

Jupiter JUNIT Version: 5.3.2

IntelliJ Version: 2019.1 Ultimate

Can anyone help.

Possible duplicate of What is a NullPointerException, and how do I fix it? — Progman
@Progman I'm not looking for nullpointer exception. This nullpointerexception is occurring within JMockit library that is a dependency for my application. This is something of a compatibility between JUNIT5 and Jmockit library. — daemon54
Please edit your question to include a minimal reproducible example, which can be compiled and tested by others. It should generate the exception you get when you execute the JUnit test. — Progman
@Progman Sure. I will post an example of this question that can be tried. — daemon54
@Progman I've added some sample code, github.com/siva54/jmockit-junit5-stackoverflow/blob/master/test/… — daemon54

daemon54 daemon54 · Accepted Answer · 2019-07-11T14:32:28

Found the issue. The issue is related to the Jmockit version that was used. The issue got resolved after I reverted the JMockit version to 1.42,

<dependency>
  <groupId>org.jmockit</groupId>
  <artifactId>jmockit</artifactId>
  <version>1.42</version>
  <scope>test</scope>
</dependency>

The issue is closely related to constructing instrumentation that can be used to reform classes to mock objects. For JMockit to run, the Jmockit JAR needs to be passed as a java agent. Prior to 1.43, If the java agent is not passed, JMockit library searches the project's dependencies and adds this to the VM object automatically. After 1.42, It was deemed by JMockit developers that this way of finding the JAR is not a good standard and is removed completely. Thereby requiring java agent to be passed manually.

Here are some reference links related to the issue,

https://github.com/jmockit/jmockit1/issues/540#issuecomment-444316617

https://github.com/jmockit/jmockit1/issues/546

https://github.com/jmockit/jmockit1/issues/568

The solution to resolving such a problem would be to

Move to version 1.42 or
Follow this sample from JMockit developers and do the same.

https://github.com/jmockit/jmockit1/blob/master/samples/petclinic/pom.xml

Getting Exception within JMockit Library when using with JUNIT5

1 Answers