Closes #16613: Added optional mapping argument to ChainMap.new_child.
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 8850e8b..dfad78e 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -112,6 +112,38 @@
self.assertEqual(dict(d), dict(a=1, b=2, c=30))
self.assertEqual(dict(d.items()), dict(a=1, b=2, c=30))
+ def test_new_child(self):
+ 'Tests for changes for issue #16613.'
+ c = ChainMap()
+ c['a'] = 1
+ c['b'] = 2
+ m = {'b':20, 'c': 30}
+ d = c.new_child(m)
+ self.assertEqual(d.maps, [{'b':20, 'c':30}, {'a':1, 'b':2}]) # check internal state
+ self.assertIs(m, d.maps[0])
+
+ # Use a different map than a dict
+ class lowerdict(dict):
+ def __getitem__(self, key):
+ if isinstance(key, str):
+ key = key.lower()
+ return dict.__getitem__(self, key)
+ def __contains__(self, key):
+ if isinstance(key, str):
+ key = key.lower()
+ return dict.__contains__(self, key)
+
+ c = ChainMap()
+ c['a'] = 1
+ c['b'] = 2
+ m = lowerdict(b=20, c=30)
+ d = c.new_child(m)
+ self.assertIs(m, d.maps[0])
+ for key in 'abc': # check contains
+ self.assertIn(key, d)
+ for k, v in dict(a=1, B=20, C=30, z=100).items(): # check get
+ self.assertEqual(d.get(k, 100), v)
+
################################################################################
### Named Tuples