public String getDiscriminatingValue(ILoggingEvent event) {
        // http://jira.qos.ch/browse/LBCLASSIC-213
        Map<String, String> mdcMap = event.getMDCPropertyMap();
        if (mdcMap == null) {
            return defaultValue;
        }
        String mdcValue = mdcMap.get(key);
        if (mdcValue == null) {
            return defaultValue;
        } else {
            return mdcValue;
        }
    }
@Test
    public void smoke() {
        logbackMDCAdapter.put(key, value);
        event = new LoggingEvent("a", logger, Level.DEBUG, "", null, null);

        String discriminatorValue = discriminator.getDiscriminatingValue(event);
        assertEquals(value, discriminatorValue);
    }