Common shuffle/shuffled with the specified random source

KT-17261, KT-9010

libraries/stdlib/test/collections/MutableCollectionsTest.kt

@@ -5,6 +5,7 @@
 
 package test.collections
 
+import kotlin.random.Random
 import kotlin.test.*
 
 
@@ -114,4 +115,16 @@ class MutableCollectionTest {
         assertEquals(list.size, shuffled.distinct().size)
     }
 
+    @Test fun shuffledPredictably() {
+        val list = List(10) { it }
+        val shuffled1 = list.shuffled(Random(1))
+        val shuffled11 = list.shuffled(Random(1))
+
+        assertEquals(shuffled1, shuffled11)
+        assertEquals("[1, 4, 0, 6, 2, 8, 9, 7, 3, 5]", shuffled1.toString())
+
+        val shuffled2 = list.shuffled(Random(42))
+        assertEquals("[5, 0, 4, 9, 2, 8, 1, 7, 6, 3]", shuffled2.toString())
+    }
+
 }