commit 170b3f79506480f78275a801822c9ff1283e16f2
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Sun Feb 11 01:09:52 2018 -0800
committer Raymond Hettinger <rhettinger@users.noreply.github.com> Sun Feb 11 01:09:52 2018 -0800
tree 26d03bec14a22b7371c189f76c4144275cdb4ecc
parent e6033209754c5b01870791645044a791da1fa73f

bpo-32792: Preserve mapping order in ChainMap() (GH-5586) (#GH-5617)

(cherry picked from commit 3793f95f98c3112ce447288a5bf9899eb9e35423)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>

Lib/test/test_collections.py

diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index a55239e..2099d23 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -141,6 +141,23 @@
         with self.assertRaises(KeyError):
             d.popitem()
 
+    def test_order_preservation(self):
+        d = ChainMap(
+                OrderedDict(j=0, h=88888),
+                OrderedDict(),
+                OrderedDict(i=9999, d=4444, c=3333),
+                OrderedDict(f=666, b=222, g=777, c=333, h=888),
+                OrderedDict(),
+                OrderedDict(e=55, b=22),
+                OrderedDict(a=1, b=2, c=3, d=4, e=5),
+                OrderedDict(),
+            )
+        self.assertEqual(''.join(d), 'abcdefghij')
+        self.assertEqual(list(d.items()),
+            [('a', 1), ('b', 222), ('c', 3333), ('d', 4444),
+             ('e', 55), ('f', 666), ('g', 777), ('h', 88888),
+             ('i', 9999), ('j', 0)])
+
     def test_dict_coercion(self):
         d = ChainMap(dict(a=1, b=2), dict(b=20, c=30))
         self.assertEqual(dict(d), dict(a=1, b=2, c=30))