    @Test
    public void testMapToPair() {

        JavaRDD<String> textRDD = sparkContext.textFile(FILE_PATH);
        List<Tuple2<String, Integer>> collect = textRDD
                .map(x -> x.split(",")[0])
                .mapToPair(x -> new Tuple2<>(x, 1)).collect();
        checkResult(collect);
    }