Fixed AccumulatorSuite to clean up SparkContext with BeforeAndAfter

core/src/test/scala/spark/AccumulatorSuite.scala

 package spark
 
+import org.scalatest.BeforeAndAfter
 import org.scalatest.FunSuite
 import org.scalatest.matchers.ShouldMatchers
 import collection.mutable
@@ -8,32 +9,39 @@ import scala.math.exp
 import scala.math.signum
 import spark.SparkContext._
 
-class AccumulatorSuite extends FunSuite with ShouldMatchers {
+class AccumulatorSuite extends FunSuite with ShouldMatchers with BeforeAndAfter {
+
+  var sc: SparkContext = null
+
+  after {
+    if (sc != null) {
+      sc.stop()
+      sc = null
+    }
+  }
 
   test ("basic accumulation"){
-    val sc = new SparkContext("local", "test")
+    sc = new SparkContext("local", "test")
     val acc : Accumulator[Int] = sc.accumulator(0)
 
     val d = sc.parallelize(1 to 20)
     d.foreach{x => acc += x}
     acc.value should be (210)
-    sc.stop()
   }
 
   test ("value not assignable from tasks") {
-    val sc = new SparkContext("local", "test")
+    sc = new SparkContext("local", "test")
     val acc : Accumulator[Int] = sc.accumulator(0)
 
     val d = sc.parallelize(1 to 20)
     evaluating {d.foreach{x => acc.value = x}} should produce [Exception]
-    sc.stop()
   }
 
   test ("add value to collection accumulators") {
     import SetAccum._
     val maxI = 1000
     for (nThreads <- List(1, 10)) { //test single & multi-threaded
-      val sc = new SparkContext("local[" + nThreads + "]", "test")
+      sc = new SparkContext("local[" + nThreads + "]", "test")
       val acc: Accumulable[mutable.Set[Any], Any] = sc.accumulable(new mutable.HashSet[Any]())
       val d = sc.parallelize(1 to maxI)
       d.foreach {
@@ -44,6 +52,7 @@ class AccumulatorSuite extends FunSuite with ShouldMatchers {
         v should contain(i)
       }
       sc.stop()
+      sc = null
     }
   }
 
@@ -67,16 +76,17 @@ class AccumulatorSuite extends FunSuite with ShouldMatchers {
     import SetAccum._
     val maxI = 1000
     for (nThreads <- List(1, 10)) { //test single & multi-threaded
-    val sc = new SparkContext("local[" + nThreads + "]", "test")
+      sc = new SparkContext("local[" + nThreads + "]", "test")
       val acc: Accumulable[mutable.Set[Any], Any] = sc.accumulable(new mutable.HashSet[Any]())
       val d = sc.parallelize(1 to maxI)
-      val thrown = evaluating {
+      evaluating {
         d.foreach {
           x => acc.value += x
         }
       } should produce [SparkException]
-      println(thrown)
+      sc.stop()
+      sc = null
     }
   }
 
-}
+}
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