diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index d785fcb..b3e0907 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -10,6 +10,7 @@
 import keyword
 import re
 import sys
+from collections import _ChainMap as ChainMap
 from collections import Hashable, Iterable, Iterator
 from collections import Sized, Container, Callable
 from collections import Set, MutableSet
@@ -17,6 +18,97 @@
 from collections import Sequence, MutableSequence
 from collections import ByteString
 
+
+################################################################################
+### _ChainMap (helper class for configparser)
+################################################################################
+
+class TestChainMap(unittest.TestCase):
+
+    def test_basics(self):
+        c = ChainMap()
+        c['a'] = 1
+        c['b'] = 2
+        d = c.new_child()
+        d['b'] = 20
+        d['c'] = 30
+        self.assertEqual(d.maps, [{'b':20, 'c':30}, {'a':1, 'b':2}])  # check internal state
+        self.assertEqual(d.items(), dict(a=1, b=20, c=30).items())    # check items/iter/getitem
+        self.assertEqual(len(d), 3)                                   # check len
+        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)
+
+        del d['b']                                                    # unmask a value
+        self.assertEqual(d.maps, [{'c':30}, {'a':1, 'b':2}])          # check internal state
+        self.assertEqual(d.items(), dict(a=1, b=2, c=30).items())     # check items/iter/getitem
+        self.assertEqual(len(d), 3)                                   # check len
+        for key in 'abc':                                             # check contains
+            self.assertIn(key, d)
+        for k, v in dict(a=1, b=2, c=30, z=100).items():              # check get
+            self.assertEqual(d.get(k, 100), v)
+        self.assertIn(repr(d), [                                      # check repr
+            type(d).__name__ + "({'c': 30}, {'a': 1, 'b': 2})",
+            type(d).__name__ + "({'c': 30}, {'b': 2, 'a': 1})"
+        ])
+
+        for e in d.copy(), copy.copy(d):                               # check shallow copies
+            self.assertEqual(d, e)
+            self.assertEqual(d.maps, e.maps)
+            self.assertIsNot(d, e)
+            self.assertIsNot(d.maps[0], e.maps[0])
+            for m1, m2 in zip(d.maps[1:], e.maps[1:]):
+                self.assertIs(m1, m2)
+
+        for e in [pickle.loads(pickle.dumps(d)),
+                  copy.deepcopy(d),
+                  eval(repr(d))
+                ]:                                                    # check deep copies
+            self.assertEqual(d, e)
+            self.assertEqual(d.maps, e.maps)
+            self.assertIsNot(d, e)
+            for m1, m2 in zip(d.maps, e.maps):
+                self.assertIsNot(m1, m2, e)
+
+        d.new_child()
+        d['b'] = 5
+        self.assertEqual(d.maps, [{'b': 5}, {'c':30}, {'a':1, 'b':2}])
+        self.assertEqual(d.parents.maps, [{'c':30}, {'a':1, 'b':2}])   # check parents
+        self.assertEqual(d['b'], 5)                                    # find first in chain
+        self.assertEqual(d.parents['b'], 2)                            # look beyond maps[0]
+
+    def test_contructor(self):
+        self.assertEqual(ChainedContext().maps, [{}])                  # no-args --> one new dict
+        self.assertEqual(ChainMap({1:2}).maps, [{1:2}])                # 1 arg --> list
+
+    def test_missing(self):
+        class DefaultChainMap(ChainMap):
+            def __missing__(self, key):
+                return 999
+        d = DefaultChainMap(dict(a=1, b=2), dict(b=20, c=30))
+        for k, v in dict(a=1, b=2, c=30, d=999).items():
+            self.assertEqual(d[k], v)                                  # check __getitem__ w/missing
+        for k, v in dict(a=1, b=2, c=30, d=77).items():
+            self.assertEqual(d.get(k, 77), v)                          # check get() w/ missing
+        for k, v in dict(a=True, b=True, c=True, d=False).items():
+            self.assertEqual(k in d, v)                                # check __contains__ w/missing
+        self.assertEqual(d.pop('a', 1001), 1, d)
+        self.assertEqual(d.pop('a', 1002), 1002)                       # check pop() w/missing
+        self.assertEqual(d.popitem(), ('b', 2))                        # check popitem() w/missing
+        with self.assertRaises(KeyError):
+            d.popitem()
+
+    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))
+        self.assertEqual(dict(d.items()), dict(a=1, b=2, c=30))
+
+
+################################################################################
+### Named Tuples
+################################################################################
+
 TestNT = namedtuple('TestNT', 'x y z')    # type used for pickle tests
 
 class TestNamedTuple(unittest.TestCase):
@@ -228,6 +320,10 @@
         self.assertEqual(repr(B(1)), 'B(x=1)')
 
 
+################################################################################
+### Abstract Base Classes
+################################################################################
+
 class ABCTestCase(unittest.TestCase):
 
     def validate_abstract_methods(self, abc, *names):
@@ -507,7 +603,7 @@
 
     def test_issue_4920(self):
         # MutableSet.pop() method did not work
-        class MySet(collections.MutableSet):
+        class MySet(MutableSet):
             __slots__=['__s']
             def __init__(self,items=None):
                 if items is None:
@@ -553,7 +649,7 @@
             self.assertTrue(issubclass(sample, Mapping))
         self.validate_abstract_methods(Mapping, '__contains__', '__iter__', '__len__',
             '__getitem__')
-        class MyMapping(collections.Mapping):
+        class MyMapping(Mapping):
             def __len__(self):
                 return 0
             def __getitem__(self, i):
@@ -625,6 +721,11 @@
         self.validate_abstract_methods(MutableSequence, '__contains__', '__iter__',
             '__len__', '__getitem__', '__setitem__', '__delitem__', 'insert')
 
+
+################################################################################
+### Counter
+################################################################################
+
 class TestCounter(unittest.TestCase):
 
     def test_basics(self):
@@ -788,6 +889,11 @@
         self.assertEqual(m,
              OrderedDict([('a', 5), ('b', 2), ('r', 2), ('c', 1), ('d', 1)]))
 
+
+################################################################################
+### OrderedDict
+################################################################################
+
 class TestOrderedDict(unittest.TestCase):
 
     def test_init(self):
@@ -1066,6 +1172,10 @@
         self.assertRaises(KeyError, d.popitem)
 
 
+################################################################################
+### Run tests
+################################################################################
+
 import doctest, collections
 
 def test_main(verbose=None):