assertTrue( s.getCurrentLockMode(s2)==LockMode.NONE );
assertTrue( s.getCurrentLockMode(s4)==LockMode.NONE );
s.lock(s1, LockMode.READ); //upgrade
assertTrue( s.getCurrentLockMode(s1)==LockMode.READ );
s.lock(s2, LockMode.UPGRADE); //upgrade
assertTrue( s.getCurrentLockMode(s2)==LockMode.UPGRADE );
s.lock(s3, LockMode.UPGRADE_NOWAIT); //upgrade
assertTrue( s.getCurrentLockMode(s3)==LockMode.UPGRADE_NOWAIT );
s.lock(s4, LockMode.NONE);
assertTrue( s.getCurrentLockMode(s4)==LockMode.NONE );