Add test that covers UnsafeShuffleSortDataFormat.swap().

Author: JoshRosen

core/src/test/java/org/apache/spark/shuffle/unsafe/UnsafeShuffleSorterSuite.java

@@ -18,6 +18,7 @@
 package org.apache.spark.shuffle.unsafe;
 
 import java.util.Arrays;
+import java.util.Random;
 
 import org.junit.Assert;
 import org.junit.Test;
@@ -107,4 +108,25 @@ public void testBasicSorting() throws Exception {
     }
     Assert.assertFalse(iter.hasNext());
   }
+
+  @Test
+  public void testSortingManyNumbers() throws Exception {
+    UnsafeShuffleSorter sorter = new UnsafeShuffleSorter(4);
+    int[] numbersToSort = new int[128000];
+    Random random = new Random(16);
+    for (int i = 0; i < numbersToSort.length; i++) {
+      numbersToSort[i] = random.nextInt(PackedRecordPointer.MAXIMUM_PARTITION_ID);
+      sorter.insertRecord(0, numbersToSort[i]);
+    }
+    Arrays.sort(numbersToSort);
+    int[] sorterResult = new int[numbersToSort.length];
+    UnsafeShuffleSorter.UnsafeShuffleSorterIterator iter = sorter.getSortedIterator();
+    int j = 0;
+    while (iter.hasNext()) {
+      iter.loadNext();
+      sorterResult[j] = iter.packedRecordPointer.getPartitionId();
+      j += 1;
+    }
+    Assert.assertArrayEquals(numbersToSort, sorterResult);
+  }
 }