Exception thrown while running JUnit tests using maven - junit4

Question

I got the following exception while running JUnit tests in Maven.
java.lang.IllegalStateException: Native library for Attach API not available in this JRE
at mockit.internal.startup.JDK6AgentLoader.getVirtualMachineImplementationFromEmbeddedOnes(JDK6AgentLoader.java:81)
at mockit.internal.startup.JDK6AgentLoader.loadAgent(JDK6AgentLoader.java:54)
at mockit.internal.startup.AgentInitialization.initializeAccordingToJDKVersion(AgentInitialization.java:21)
at mockit.internal.startup.Startup.initializeIfNeeded(Startup.java:96)
at mockit.integration.junit4.JMockit.<clinit>(JMockit.java:23)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:31)
at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:24)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)
at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:29)
at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)
at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:24)
at org.apache.maven.surefire.junit4.JUnit4TestSet.<init>(JUnit4TestSet.java:45)
at org.apache.maven.surefire.junit4.JUnit4DirectoryTestSuite.createTestSet(JUnit4DirectoryTestSuite.java:56)
at org.apache.maven.surefire.suite.AbstractDirectoryTestSuite.locateTestSets(AbstractDirectoryTestSuite.java:96)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.maven.surefire.booter.SurefireBooter.getTestSets(SurefireBooter.java:455)
at org.apache.maven.surefire.booter.SurefireBooter.runSuitesForkPerTestSet(SurefireBooter.java:406)
at org.apache.maven.surefire.booter.SurefireBooter.run(SurefireBooter.java:249)
at org.apache.maven.plugin.surefire.SurefirePlugin.execute(SurefirePlugin.java:537)
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:556)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:535)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:348)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:60)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
Caused by: java.lang.UnsatisfiedLinkError: Native Library C:\Program Files\Java\jdk1.6.0_25\jre\bin\attach.dll already loaded in another classloader
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1772)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1724)
at java.lang.Runtime.loadLibrary0(Runtime.java:823)
at java.lang.System.loadLibrary(System.java:1028)
at sun.tools.attach.WindowsVirtualMachine.<clinit>(WindowsVirtualMachine.java:169)
at mockit.internal.startup.JDK6AgentLoader.getVirtualMachineImplementationFromEmbeddedOnes(JDK6AgentLoader.java:68)
... 44 more
I have used mocking in my tests.The framework used is JMockit. Any help is appreciated.

Answer 1

I don't know why this duplicate loading of "attach.dll" occurs (will investigate later), but you can avoid the problem by using the "-javaagent" JVM initialization parameter. See here for details.

Answer 2

I'll give it a try. Here it says something like:
Caused by: java.lang.UnsatisfiedLinkError: Native Library C:\Program Files\Java\jdk1.6.0_25\jre\bin\attach.dll already loaded in another classloader
My guess is that you try to load the dll twice? Once maybe it's loaded as a maven dependency and once as from the jdk?

Answer 3

Try adding tools.jar to your classpath. If you've downloaded a JDK, it is typically in Contents/Home/lib/tools.jar under your JDK root. If you're using Eclipse, check out this answer on another question.