The test fails with the virtual test thread factory because it tries to find the "main" thread in the list of threads returned by JDI, but "main" is a virtual thread and will only be returned by JDI if the debug agent is launched with includevirtualthreads=y. As a result the thread is not found and the test asserts:

java.lang.RuntimeException: assertTrue: expected true, was false
at jdk.test.lib.Asserts.fail(Asserts.java:594)
at jdk.test.lib.Asserts.assertTrue(Asserts.java:486)
at jdk.test.lib.Asserts.assertTrue(Asserts.java:472)
at TestNestmateAttr.checkGoodTransforms(TestNestmateAttr.java:511)
at TestNestmateAttr.methodEntered(TestNestmateAttr.java:320)
at TestScaffold$EventHandler.notifyEvent(TestScaffold.java:205)
at TestScaffold$EventHandler.run(TestScaffold.java:279)
at java.base/java.lang.Thread.run(Thread.java:1583)