public synchronized void setLevel(Level newLevel) {
        if (level == newLevel) {
            // nothing to do;
            return;
        }
        if (newLevel == null && isRootLogger()) {
            throw new IllegalArgumentException("The level of the root logger cannot be set to null");
        }

        level = newLevel;
        if (newLevel == null) {
            effectiveLevelInt = parent.effectiveLevelInt;
            newLevel = parent.getEffectiveLevel();
        } else {
            effectiveLevelInt = newLevel.levelInt;
        }

        if (childrenList != null) {
            int len = childrenList.size();
            for (int i = 0; i < len; i++) {
                Logger child = (Logger) childrenList.get(i);
                // tell child to handle parent levelInt change
                child.handleParentLevelChange(effectiveLevelInt);
            }
        }
        // inform listeners
        loggerContext.fireOnLevelChange(this, newLevel);
    }
@Test
    public void testEnabledX_Warn() throws Exception {
        root.setLevel(Level.WARN);
        checkLevelThreshold(loggerTest, Level.WARN);
    }