Not working under OpenJ9

Environment:
openjdk 11.0.1 2018-10-16
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.1+13)
Eclipse OpenJ9 VM AdoptOpenJDK (build openj9-0.11.0, JRE 11 Mac OS X amd64-64-Bit Compressed References 20181115_16 (JIT enabled, AOT enabled)

OpenJ9 - 090ff9dcd
OMR - ea548a66
JCL - d4455071ce based on jdk-11.0.1+13)

Stacktrace:

org.gradle.api.internal.tasks.testing.TestSuiteExecutionException: Could not complete execution for Gradle Test Executor 10.
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:63)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
    at com.sun.proxy.$Proxy4.stop(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.stop(TestWorker.java:132)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:175)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:157)
    at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:404)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
    at java.base/java.lang.Thread.run(Thread.java:825)
Caused by: java.util.ServiceConfigurationError: org.junit.platform.launcher.TestExecutionListener: Provider reactor.blockhound.junit.platform.BlockHoundTestExecutionListener could not be instantiated
    at java.base/java.util.ServiceLoader.fail(ServiceLoader.java:581)
    at java.base/java.util.ServiceLoader$ProviderImpl.newInstance(ServiceLoader.java:803)
    at java.base/java.util.ServiceLoader$ProviderImpl.get(ServiceLoader.java:721)
    at java.base/java.util.ServiceLoader$3.next(ServiceLoader.java:1394)
    at java.base/java.lang.Iterable.forEach(Iterable.java:74)
    at org.junit.platform.launcher.core.LauncherFactory.create(LauncherFactory.java:94)
    at org.junit.platform.launcher.core.LauncherFactory.create(LauncherFactory.java:67)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.processAllTestClasses(JUnitPlatformTestClassProcessor.java:100)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.access$000(JUnitPlatformTestClassProcessor.java:82)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.stop(JUnitPlatformTestClassProcessor.java:78)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.stop(SuiteTestClassProcessor.java:61)
    ... 25 more
Caused by: java.lang.ExceptionInInitializerError
    at java.base/java.lang.J9VMInternals.ensureError(J9VMInternals.java:191)
    at java.base/java.lang.J9VMInternals.recordInitializationFailure(J9VMInternals.java:180)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
    at java.base/java.util.ServiceLoader$ProviderImpl.newInstance(ServiceLoader.java:779)
    ... 34 more
Caused by: java.lang.RuntimeException: java.lang.instrument.UnmodifiableClassException
    at reactor.BlockHound$Builder.install(BlockHound.java:264)
    at reactor.BlockHound.install(BlockHound.java:64)
    at reactor.blockhound.junit.platform.BlockHoundTestExecutionListener.<clinit>(BlockHoundTestExecutionListener.java:12)
    ... 39 more
Caused by: java.lang.instrument.UnmodifiableClassException
    at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
    at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:167)
    at reactor.BlockHound$Builder.instrument(BlockHound.java:273)
    at reactor.BlockHound$Builder.install(BlockHound.java:261)
    ... 41 more

Start by reproducing the Gradle test failure under the reported OpenJ9 and Java 11 environment. Read reactor.blockhound.junit.platform.BlockHoundTestExecutionListener and the BlockHound$Builder.install/instrument stack-trace locations to investigate the UnmodifiableClassException. Done means the test listener can initialize and the test suite completes successfully under OpenJ9.