apache-spark 字数单元测试（Scala + JUnit）
示例
例如，我们有WordCountServicewithcountWords方法：
class WordCountService {
def countWords(url: String): Map[String, Int] = {
val sparkConf = new SparkConf().setMaster("spark://somehost:7077").setAppName("WordCount"))
val sc = new SparkContext(sparkConf)
val textFile = sc.textFile(url)
textFile.flatMap(line => line.split(" "))
.map(word => (word, 1))
.reduceByKey(_ + _).collect().toMap
}
}这项服务看起来很丑陋，不适合单元测试。应该将SparkContext注入此服务。可以使用您最喜欢的DI框架来实现，但为简单起见，它将使用构造函数实现：
class WordCountService(val sc: SparkContext) {
def countWords(url: String): Map[String, Int] = {
val textFile = sc.textFile(url)
textFile.flatMap(line => line.split(" "))
.map(word => (word, 1))
.reduceByKey(_ + _).collect().toMap
}
}现在我们可以创建简单的JUnit测试并将可测试的sparkContext注入WordCountService：
class WordCountServiceTest {
val sparkConf = new SparkConf().setMaster("local[*]").setAppName("WordCountTest")
val testContext = new SparkContext(sparkConf)
val wordCountService = new WordCountService(testContext)
@Test
def countWordsTest() {
val testFilePath = "file://my-test-file.txt"
val counts = wordCountService.countWords(testFilePath)
Assert.assertEquals(counts("dog"), 121)
Assert.assertEquals(counts("cat"), 191)
}
}