Currently, jtreg incorrectly confuses the concept of the /directory/ in which the test's class will be written with the /classpath/ used to locate all of the test's classes, including any library classes. It provides env variable TESTCLASSES and system property test.classes, and tests use these to mean both a directory and a classpath.
jtreg will be fixed to separate the two concepts, such that TESTCLASSES/test.classes will continue to mean the /directory/ in which the test's class will the written, and will introduce TESTCLASSPATH/test.class.path for the classpath used to locate all the test's classes.
This change only affects a small number of tests, which use both @library and TESTCLASSES. A number of serviceability tests are affected,
However, all the failures are caused by issues in shared library code, meaning that only that code needs to be updated.