private void setupAndCheckLevels(String levelString, String expectedOnOffString, Level shouldLog, Level shouldNotLog) {
        try {
            if (levelString != null) {
                System.setProperty("vespa.log.level", levelString);
            }
            LogSetup.initVespaLogging("TST");
            Logger.getLogger("TEST").log(LogLevel.DEBUG, "DEBUG");
            LevelController levelController = LogSetup.getLogHandler().getLevelControl("TST");
            assertNotNull(levelController);
            assertEquals(expectedOnOffString, levelController.getOnOffString());
            if (shouldLog != null) {
                assertTrue(levelController.shouldLog(shouldLog));
            }
            if (shouldNotLog != null) {
                assertFalse(levelController.shouldLog(shouldNotLog));
            }
        } finally {
            LogSetup.clearHandlers();
        }
    }
Make sure we can install the logging stuff properly.

@author Bjorn Borud
vespalog/src/test/java/com/yahoo/log/LogSetupTestCase.java