If for example the test is run as

jtreg -s -w:/tmp -r:/tmp -va -Dtest.dir=/Volumes/Diverse -dir:./test/jdk java/nio/file/Files/CopyAndMove.java

when test.dir specifies a different device from that on which the directory in which the test is run is located then several sub-tests fail, for example:

STDOUT:
Seed from RandomFactory = 5881992636870125551L
STDERR:
java.lang.RuntimeException: Assertion failed
at CopyAndMove.assertTrue(CopyAndMove.java:1114)
at CopyAndMove.checkPosixAttributes(CopyAndMove.java:119)
at CopyAndMove.moveAndVerify(CopyAndMove.java:229)
at CopyAndMove.testMove(CopyAndMove.java:267)
at CopyAndMove.main(CopyAndMove.java:69)
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 com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:115)
at java.base/java.lang.Thread.run(Thread.java:832)

The specific sub-tests which fail are marked with "//XXX" in the webrev at http://cr.openjdk.java.net/~bpb/8203803/failed-sub-tests/.