### Question:
QMUX extends QBeanSupport implements SpaceListener, MUX, QMUXMBean, Loggeable, MetricsProvider { public synchronized void setUnhandledQueue (String unhandled) { this.unhandled = unhandled; getPersist().getChild("unhandled").setText (unhandled); setModified (true); } QMUX(); void initService(); void startService(); void stopService(); void destroyService(); static MUX getMUX(String name); ISOMsg request(ISOMsg m, long timeout); void request(ISOMsg m, long timeout, ISOResponseListener rl, Object handBack); @Override void notify(Object k, Object value); String getKey(ISOMsg m); @Override Metrics getMetrics(); synchronized void setInQueue(String in); String getInQueue(); synchronized void setOutQueue(String out); String getOutQueue(); Space getSpace(); synchronized void setUnhandledQueue(String unhandled); String getUnhandledQueue(); @SuppressWarnings("unused") String[] getReadyIndicatorNames(); void addISORequestListener(ISORequestListener l); boolean removeISORequestListener(ISORequestListener l); synchronized void resetCounters(); String getCountersAsString(); int getTXCounter(); int getRXCounter(); @Override int getTXExpired(); @Override int getTXPending(); @Override int getRXExpired(); @Override int getRXPending(); @Override int getRXUnhandled(); @Override int getRXForwarded(); long getLastTxnTimestampInMillis(); long getIdleTimeInMillis(); void send(ISOMsg m); boolean isConnected(); void dump(PrintStream p, String indent);  }### Answer:
@Test public void testSetUnhandledQueueThrowsNullPointerException() throws Throwable { QMUX qMUX = new QMUX(); try { qMUX.setUnhandledQueue("testQMUXUnhandled"); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { assertEquals("testQMUXUnhandled", qMUX.unhandled, "qMUX.unhandled"); if (isJavaVersionAtMost(JAVA_14)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Cannot invoke \"org.jdom2.Element.getChild(String)\" because the return value of \"org.jpos.q2.iso.QMUX.getPersist()\" is null", ex.getMessage(), "ex.getMessage()"); } assertFalse(qMUX.isModified(), "qMUX.isModified()"); } }