#vulnerable code 
                                @Test
    public void tokenExpiredAfterOpenButBeforeSendHttp() throws InvalidKeyException, IOException, InterruptedException, URISyntaxException
    {
        final long SECONDS_FOR_SAS_TOKEN_TO_LIVE = 3;
        final long MILLISECONDS_TO_WAIT_FOR_TOKEN_TO_EXPIRE = 5000;

        if (testInstance.protocol != HTTPS || testInstance.authenticationType != SAS)
        {
            //This scenario only applies to HTTP since MQTT and AMQP allow expired sas tokens for 30 minutes after open
            // as long as token did not expire before open. X509 doesn't apply either
            return;
        }

        String soonToBeExpiredSASToken = generateSasTokenForIotDevice(hostName, testInstance.identity.getDeviceId(), testInstance.identity.getPrimaryKey(), SECONDS_FOR_SAS_TOKEN_TO_LIVE);
        DeviceClient client = new DeviceClient(soonToBeExpiredSASToken, testInstance.protocol);
        IotHubServicesCommon.openClientWithRetry(client);

        //Force the SAS token to expire before sending messages
        Thread.sleep(MILLISECONDS_TO_WAIT_FOR_TOKEN_TO_EXPIRE);
        IotHubServicesCommon.sendMessagesExpectingSASTokenExpiration(client, testInstance.protocol.toString(), 1, RETRY_MILLISECONDS, SEND_TIMEOUT_MILLISECONDS, testInstance.authenticationType);
        client.closeNow();
    } 
                            #location 14 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void tokenExpiredAfterOpenButBeforeSendHttp() throws Exception
    {
        final long SECONDS_FOR_SAS_TOKEN_TO_LIVE = 3;
        final long MILLISECONDS_TO_WAIT_FOR_TOKEN_TO_EXPIRE = 5000;

        if (testInstance.protocol != HTTPS || testInstance.authenticationType != SAS)
        {
            //This scenario only applies to HTTP since MQTT and AMQP allow expired sas tokens for 30 minutes after open
            // as long as token did not expire before open. X509 doesn't apply either
            return;
        }

        this.testInstance.setup();

        String soonToBeExpiredSASToken = generateSasTokenForIotDevice(hostName, testInstance.identity.getDeviceId(), testInstance.identity.getPrimaryKey(), SECONDS_FOR_SAS_TOKEN_TO_LIVE);
        DeviceClient client = new DeviceClient(soonToBeExpiredSASToken, testInstance.protocol);
        IotHubServicesCommon.openClientWithRetry(client);

        //Force the SAS token to expire before sending messages
        Thread.sleep(MILLISECONDS_TO_WAIT_FOR_TOKEN_TO_EXPIRE);
        IotHubServicesCommon.sendMessagesExpectingSASTokenExpiration(client, testInstance.protocol.toString(), 1, RETRY_MILLISECONDS, SEND_TIMEOUT_MILLISECONDS, testInstance.authenticationType);
        client.closeNow();
    }