test log snippet:
"MainThread" #31 [1560215] prio=5 os_prio=0 cpu=112.94ms elapsed=480.14s tid=0x00007f5cc41e82c0 nid=1560215 waiting on condition [0x00007f5c6fa27000]
   java.lang.Thread.State: WAITING (parking)
at jdk.internal.misc.Unsafe.park(java.base@24/Native Method)
- parking to wait for <0x000000011bbc0e80> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(java.base@24/LockSupport.java:371)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionNode.block(java.base@24/AbstractQueuedSynchronizer.java:519)
at java.util.concurrent.ForkJoinPool.unmanagedBlock(java.base@24/ForkJoinPool.java:4021)
at java.util.concurrent.ForkJoinPool.managedBlock(java.base@24/ForkJoinPool.java:3967)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(java.base@24/AbstractQueuedSynchronizer.java:1712)
at java.lang.ProcessImpl.waitFor(java.base@24/ProcessImpl.java:425)
at TestScaffold.waitForVMDisconnect(TestScaffold.java:781)
- locked <0x000000011b7fe0f8> (a BreakpointOnClassPrepare)
at TestScaffold.resumeToVMDisconnect(TestScaffold.java:1015)
at TestScaffold.listenUntilVMDisconnect(TestScaffold.java:743)
at BreakpointOnClassPrepare.runTests(BreakpointOnClassPrepare.java:148)
at TestScaffold.startTests(TestScaffold.java:468)
at BreakpointOnClassPrepare.main(BreakpointOnClassPrepare.java:96)

Got BreakpointEvent: 1 for thread instance of java.lang.Thread(name='MyThread-1', id=335)
Timeout signalled after 480 seconds
STDERR:
[1ms] run args: [BreakpointOnClassPrepareTarg, SUSPEND_NONE]
[173ms] Got ClassPrepareEvent: ClassPrepareEvent in thread MyThread-1
[224ms] FAILED: Exception occured in eventHandler: com.sun.jdi.ObjectCollectedException
at java.base/java.lang.Thread.getStackTrace(Thread.java:2389)
at TestScaffold.failure(TestScaffold.java:491)
at TestScaffold$EventHandler.run(TestScaffold.java:298)
at java.base/java.lang.Thread.run(Thread.java:1575)
com.sun.jdi.ObjectCollectedException
at jdk.jdi/com.sun.tools.jdi.JDWPException.toJDIException(JDWPException.java:56)
at jdk.jdi/com.sun.tools.jdi.ObjectReferenceImpl.referenceType(ObjectReferenceImpl.java:174)
at jdk.jdi/com.sun.tools.jdi.ThreadReferenceImpl.toString(ThreadReferenceImpl.java:636)
at java.base/java.lang.String.valueOf(String.java:4556)
at BreakpointOnClassPrepare.breakpointReached(BreakpointOnClassPrepare.java:107)
at TestScaffold$EventHandler.notifyEvent(TestScaffold.java:193)
at TestScaffold$EventHandler.run(TestScaffold.java:277)
at java.base/java.lang.Thread.run(Thread.java:1575)