#fixed code
                                @Test (expected = IllegalArgumentException.class)
    public void request_nullHttpMethod_failed() throws Exception
    {
        //arrange

        //act
        HttpResponse response = DeviceOperations.request(
                IOT_HUB_CONNECTION_STRING,
                new URL(STANDARD_URL),
                null,
                STANDARD_PAYLOAD,
                STANDARD_REQUEST_ID,
                0);

        //assert
    }
#vulnerable code 
                                @Test (expected = IllegalArgumentException.class)
    public void request_nullHttpMethod_failed() throws Exception
    {
        //arrange

        //act
        HttpResponse response = DeviceOperations.request(
                IOT_HUB_CONNECTION_STRING,
                new URL(STANDARD_URL),
                null,
                STANDARD_PAYLOAD,
                STANDARD_REQUEST_ID);

        //assert
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE