From 01b9881062b5f751e5e5a60b87935a09dd92e8e4 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Mon, 19 Feb 2007 07:30:21 +0000
Subject: [PATCH] Add test for merge stability

---
 Lib/test/test_heapq.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Lib/test/test_heapq.py b/Lib/test/test_heapq.py
index b7c3ab2f12d..b2bbfab0fa1 100644
--- a/Lib/test/test_heapq.py
+++ b/Lib/test/test_heapq.py
@@ -111,6 +111,21 @@ class TestHeap(unittest.TestCase):
         self.assertEqual(sorted(chain(*inputs)), list(merge(*inputs)))
         self.assertEqual(list(merge()), [])
 
+    def test_merge_stability(self):
+        class Int(int):
+            pass
+        inputs = [[], [], [], []]
+        for i in range(20000):
+            stream = random.randrange(4)
+            x = random.randrange(500)
+            obj = Int(x)
+            obj.pair = (x, stream)
+            inputs[stream].append(obj)
+        for stream in inputs:
+            stream.sort()
+        result = [i.pair for i in merge(*inputs)]
+        self.assertEqual(result, sorted(result))
+
     def test_nsmallest(self):
         data = [(random.randrange(2000), i) for i in range(1000)]
         for f in (None, lambda x:  x[0] * 547 % 2000):