Merge pull request scala#1396 from axel22/issue/6410

SI-6410 add test cases.

Author: jsuereth

test/files/run/t6410.check

@@ -0,0 +1,2 @@
+ParMap(0 -> 4, 1 -> 5)
+ParMap(0 -> 4, 1 -> 5)

test/files/run/t6410.scala

@@ -0,0 +1,9 @@
+
+
+
+object Test extends App {
+  val x = collection.parallel.mutable.ParArray.range(1,10) groupBy { _ % 2 } mapValues { _.size }
+  println(x)
+  val y = collection.parallel.immutable.ParVector.range(1,10) groupBy { _ % 2 } mapValues { _.size }
+  println(y)
+}