#vulnerable code 
                                @Test
    public void testJmsQueueAppenderCompatibility() throws Exception {
        assertEquals(0, queue.size());
        final JmsAppender appender = (JmsAppender) ctx.getRequiredAppender("JmsQueueAppender");
        final LogEvent expected = createLogEvent();
        appender.append(expected);
        assertEquals(1, queue.size());
        final Message message = queue.getMessageAt(0);
        assertNotNull(message);
        assertThat(message, instanceOf(ObjectMessage.class));
        final ObjectMessage objectMessage = (ObjectMessage) message;
        final Object o = objectMessage.getObject();
        assertThat(o, instanceOf(LogEvent.class));
        final LogEvent actual = (LogEvent) o;
        assertEquals(expected.getMessage().getFormattedMessage(), actual.getMessage().getFormattedMessage());
    } 
                            #location 15 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testJmsQueueAppenderCompatibility() throws Exception {
        final JmsAppender appender = (JmsAppender) ctx.getRequiredAppender("JmsQueueAppender");
        final LogEvent expected = createLogEvent();
        appender.append(expected);
        then(session).should().createObjectMessage(eq(expected));
        then(objectMessage).should().setJMSTimestamp(anyLong());
        then(messageProducer).should().send(objectMessage);
        appender.stop();
        then(session).should().close();
        then(connection).should().close();
    }