4.6. Should a test call the System.exit method?

NO! The default harness security manager prevents tests from calling System.exit. If the test is running in the same JVM as the harness and the harness was not permitted to install its own security manager, a call to System.exit will cause the harness itself to exit!

If the test is running in its own separate JVM, a call to System.exit may not allow the harness to properly handle test termination.