diff --git a/Lib/test/multibytecodec_support.py b/Lib/test/multibytecodec_support.py
new file mode 100644
index 0000000..a2c57ea
--- /dev/null
+++ b/Lib/test/multibytecodec_support.py
@@ -0,0 +1,372 @@
+#!/usr/bin/env python3
+#
+# multibytecodec_support.py
+#   Common Unittest Routines for CJK codecs
+#
+
+import codecs
+import os
+import re
+import sys
+import unittest
+from http.client import HTTPException
+from test import support
+from io import BytesIO
+
+class TestBase:
+    encoding        = ''   # codec name
+    codec           = None # codec tuple (with 4 elements)
+    tstring         = None # must set. 2 strings to test StreamReader
+
+    codectests      = None # must set. codec test tuple
+    roundtriptest   = 1    # set if roundtrip is possible with unicode
+    has_iso10646    = 0    # set if this encoding contains whole iso10646 map
+    xmlcharnametest = None # string to test xmlcharrefreplace
+    unmappedunicode = '\udeee' # a unicode codepoint that is not mapped.
+
+    def setUp(self):
+        if self.codec is None:
+            self.codec = codecs.lookup(self.encoding)
+        self.encode = self.codec.encode
+        self.decode = self.codec.decode
+        self.reader = self.codec.streamreader
+        self.writer = self.codec.streamwriter
+        self.incrementalencoder = self.codec.incrementalencoder
+        self.incrementaldecoder = self.codec.incrementaldecoder
+
+    def test_chunkcoding(self):
+        tstring_lines = []
+        for b in self.tstring:
+            lines = b.split(b"\n")
+            last = lines.pop()
+            assert last == b""
+            lines = [line + b"\n" for line in lines]
+            tstring_lines.append(lines)
+        for native, utf8 in zip(*tstring_lines):
+            u = self.decode(native)[0]
+            self.assertEqual(u, utf8.decode('utf-8'))
+            if self.roundtriptest:
+                self.assertEqual(native, self.encode(u)[0])
+
+    def test_errorhandle(self):
+        for source, scheme, expected in self.codectests:
+            if isinstance(source, bytes):
+                func = self.decode
+            else:
+                func = self.encode
+            if expected:
+                result = func(source, scheme)[0]
+                if func is self.decode:
+                    self.assertTrue(type(result) is str, type(result))
+                    self.assertEqual(result, expected,
+                                     '%a.decode(%r, %r)=%a != %a'
+                                     % (source, self.encoding, scheme, result,
+                                        expected))
+                else:
+                    self.assertTrue(type(result) is bytes, type(result))
+                    self.assertEqual(result, expected,
+                                     '%a.encode(%r, %r)=%a != %a'
+                                     % (source, self.encoding, scheme, result,
+                                        expected))
+            else:
+                self.assertRaises(UnicodeError, func, source, scheme)
+
+    def test_xmlcharrefreplace(self):
+        if self.has_iso10646:
+            return
+
+        s = "\u0b13\u0b23\u0b60 nd eggs"
+        self.assertEqual(
+            self.encode(s, "xmlcharrefreplace")[0],
+            b"&#2835;&#2851;&#2912; nd eggs"
+        )
+
+    def test_customreplace_encode(self):
+        if self.has_iso10646:
+            return
+
+        from html.entities import codepoint2name
+
+        def xmlcharnamereplace(exc):
+            if not isinstance(exc, UnicodeEncodeError):
+                raise TypeError("don't know how to handle %r" % exc)
+            l = []
+            for c in exc.object[exc.start:exc.end]:
+                if ord(c) in codepoint2name:
+                    l.append("&%s;" % codepoint2name[ord(c)])
+                else:
+                    l.append("&#%d;" % ord(c))
+            return ("".join(l), exc.end)
+
+        codecs.register_error("test.xmlcharnamereplace", xmlcharnamereplace)
+
+        if self.xmlcharnametest:
+            sin, sout = self.xmlcharnametest
+        else:
+            sin = "\xab\u211c\xbb = \u2329\u1234\u232a"
+            sout = b"&laquo;&real;&raquo; = &lang;&#4660;&rang;"
+        self.assertEqual(self.encode(sin,
+                                    "test.xmlcharnamereplace")[0], sout)
+
+    def test_callback_wrong_objects(self):
+        def myreplace(exc):
+            return (ret, exc.end)
+        codecs.register_error("test.cjktest", myreplace)
+
+        for ret in ([1, 2, 3], [], None, object(), b'string', b''):
+            self.assertRaises(TypeError, self.encode, self.unmappedunicode,
+                              'test.cjktest')
+
+    def test_callback_long_index(self):
+        def myreplace(exc):
+            return ('x', int(exc.end))
+        codecs.register_error("test.cjktest", myreplace)
+        self.assertEqual(self.encode('abcd' + self.unmappedunicode + 'efgh',
+                                     'test.cjktest'), (b'abcdxefgh', 9))
+
+        def myreplace(exc):
+            return ('x', sys.maxsize + 1)
+        codecs.register_error("test.cjktest", myreplace)
+        self.assertRaises(IndexError, self.encode, self.unmappedunicode,
+                          'test.cjktest')
+
+    def test_callback_None_index(self):
+        def myreplace(exc):
+            return ('x', None)
+        codecs.register_error("test.cjktest", myreplace)
+        self.assertRaises(TypeError, self.encode, self.unmappedunicode,
+                          'test.cjktest')
+
+    def test_callback_backward_index(self):
+        def myreplace(exc):
+            if myreplace.limit > 0:
+                myreplace.limit -= 1
+                return ('REPLACED', 0)
+            else:
+                return ('TERMINAL', exc.end)
+        myreplace.limit = 3
+        codecs.register_error("test.cjktest", myreplace)
+        self.assertEqual(self.encode('abcd' + self.unmappedunicode + 'efgh',
+                                     'test.cjktest'),
+                (b'abcdREPLACEDabcdREPLACEDabcdREPLACEDabcdTERMINALefgh', 9))
+
+    def test_callback_forward_index(self):
+        def myreplace(exc):
+            return ('REPLACED', exc.end + 2)
+        codecs.register_error("test.cjktest", myreplace)
+        self.assertEqual(self.encode('abcd' + self.unmappedunicode + 'efgh',
+                                     'test.cjktest'), (b'abcdREPLACEDgh', 9))
+
+    def test_callback_index_outofbound(self):
+        def myreplace(exc):
+            return ('TERM', 100)
+        codecs.register_error("test.cjktest", myreplace)
+        self.assertRaises(IndexError, self.encode, self.unmappedunicode,
+                          'test.cjktest')
+
+    def test_incrementalencoder(self):
+        UTF8Reader = codecs.getreader('utf-8')
+        for sizehint in [None] + list(range(1, 33)) + \
+                        [64, 128, 256, 512, 1024]:
+            istream = UTF8Reader(BytesIO(self.tstring[1]))
+            ostream = BytesIO()
+            encoder = self.incrementalencoder()
+            while 1:
+                if sizehint is not None:
+                    data = istream.read(sizehint)
+                else:
+                    data = istream.read()
+
+                if not data:
+                    break
+                e = encoder.encode(data)
+                ostream.write(e)
+
+            self.assertEqual(ostream.getvalue(), self.tstring[0])
+
+    def test_incrementaldecoder(self):
+        UTF8Writer = codecs.getwriter('utf-8')
+        for sizehint in [None, -1] + list(range(1, 33)) + \
+                        [64, 128, 256, 512, 1024]:
+            istream = BytesIO(self.tstring[0])
+            ostream = UTF8Writer(BytesIO())
+            decoder = self.incrementaldecoder()
+            while 1:
+                data = istream.read(sizehint)
+                if not data:
+                    break
+                else:
+                    u = decoder.decode(data)
+                    ostream.write(u)
+
+            self.assertEqual(ostream.getvalue(), self.tstring[1])
+
+    def test_incrementalencoder_error_callback(self):
+        inv = self.unmappedunicode
+
+        e = self.incrementalencoder()
+        self.assertRaises(UnicodeEncodeError, e.encode, inv, True)
+
+        e.errors = 'ignore'
+        self.assertEqual(e.encode(inv, True), b'')
+
+        e.reset()
+        def tempreplace(exc):
+            return ('called', exc.end)
+        codecs.register_error('test.incremental_error_callback', tempreplace)
+        e.errors = 'test.incremental_error_callback'
+        self.assertEqual(e.encode(inv, True), b'called')
+
+        # again
+        e.errors = 'ignore'
+        self.assertEqual(e.encode(inv, True), b'')
+
+    def test_streamreader(self):
+        UTF8Writer = codecs.getwriter('utf-8')
+        for name in ["read", "readline", "readlines"]:
+            for sizehint in [None, -1] + list(range(1, 33)) + \
+                            [64, 128, 256, 512, 1024]:
+                istream = self.reader(BytesIO(self.tstring[0]))
+                ostream = UTF8Writer(BytesIO())
+                func = getattr(istream, name)
+                while 1:
+                    data = func(sizehint)
+                    if not data:
+                        break
+                    if name == "readlines":
+                        ostream.writelines(data)
+                    else:
+                        ostream.write(data)
+
+                self.assertEqual(ostream.getvalue(), self.tstring[1])
+
+    def test_streamwriter(self):
+        readfuncs = ('read', 'readline', 'readlines')
+        UTF8Reader = codecs.getreader('utf-8')
+        for name in readfuncs:
+            for sizehint in [None] + list(range(1, 33)) + \
+                            [64, 128, 256, 512, 1024]:
+                istream = UTF8Reader(BytesIO(self.tstring[1]))
+                ostream = self.writer(BytesIO())
+                func = getattr(istream, name)
+                while 1:
+                    if sizehint is not None:
+                        data = func(sizehint)
+                    else:
+                        data = func()
+
+                    if not data:
+                        break
+                    if name == "readlines":
+                        ostream.writelines(data)
+                    else:
+                        ostream.write(data)
+
+                self.assertEqual(ostream.getvalue(), self.tstring[0])
+
+
+class TestBase_Mapping(unittest.TestCase):
+    pass_enctest = []
+    pass_dectest = []
+    supmaps = []
+    codectests = []
+
+    def __init__(self, *args, **kw):
+        unittest.TestCase.__init__(self, *args, **kw)
+        try:
+            self.open_mapping_file().close() # test it to report the error early
+        except (IOError, HTTPException):
+            self.skipTest("Could not retrieve "+self.mapfileurl)
+
+    def open_mapping_file(self):
+        return support.open_urlresource(self.mapfileurl)
+
+    def test_mapping_file(self):
+        if self.mapfileurl.endswith('.xml'):
+            self._test_mapping_file_ucm()
+        else:
+            self._test_mapping_file_plain()
+
+    def _test_mapping_file_plain(self):
+        unichrs = lambda s: ''.join(map(chr, map(eval, s.split('+'))))
+        urt_wa = {}
+
+        with self.open_mapping_file() as f:
+            for line in f:
+                if not line:
+                    break
+                data = line.split('#')[0].strip().split()
+                if len(data) != 2:
+                    continue
+
+                csetval = eval(data[0])
+                if csetval <= 0x7F:
+                    csetch = bytes([csetval & 0xff])
+                elif csetval >= 0x1000000:
+                    csetch = bytes([(csetval >> 24), ((csetval >> 16) & 0xff),
+                                    ((csetval >> 8) & 0xff), (csetval & 0xff)])
+                elif csetval >= 0x10000:
+                    csetch = bytes([(csetval >> 16), ((csetval >> 8) & 0xff),
+                                    (csetval & 0xff)])
+                elif csetval >= 0x100:
+                    csetch = bytes([(csetval >> 8), (csetval & 0xff)])
+                else:
+                    continue
+
+                unich = unichrs(data[1])
+                if ord(unich) == 0xfffd or unich in urt_wa:
+                    continue
+                urt_wa[unich] = csetch
+
+                self._testpoint(csetch, unich)
+
+    def _test_mapping_file_ucm(self):
+        with self.open_mapping_file() as f:
+            ucmdata = f.read()
+        uc = re.findall('<a u="([A-F0-9]{4})" b="([0-9A-F ]+)"/>', ucmdata)
+        for uni, coded in uc:
+            unich = chr(int(uni, 16))
+            codech = bytes(int(c, 16) for c in coded.split())
+            self._testpoint(codech, unich)
+
+    def test_mapping_supplemental(self):
+        for mapping in self.supmaps:
+            self._testpoint(*mapping)
+
+    def _testpoint(self, csetch, unich):
+        if (csetch, unich) not in self.pass_enctest:
+            self.assertEqual(unich.encode(self.encoding), csetch)
+        if (csetch, unich) not in self.pass_dectest:
+            self.assertEqual(str(csetch, self.encoding), unich)
+
+    def test_errorhandle(self):
+        for source, scheme, expected in self.codectests:
+            if isinstance(source, bytes):
+                func = source.decode
+            else:
+                func = source.encode
+            if expected:
+                if isinstance(source, bytes):
+                    result = func(self.encoding, scheme)
+                    self.assertTrue(type(result) is str, type(result))
+                    self.assertEqual(result, expected,
+                                     '%a.decode(%r, %r)=%a != %a'
+                                     % (source, self.encoding, scheme, result,
+                                        expected))
+                else:
+                    result = func(self.encoding, scheme)
+                    self.assertTrue(type(result) is bytes, type(result))
+                    self.assertEqual(result, expected,
+                                     '%a.encode(%r, %r)=%a != %a'
+                                     % (source, self.encoding, scheme, result,
+                                        expected))
+            else:
+                self.assertRaises(UnicodeError, func, self.encoding, scheme)
+
+def load_teststring(name):
+    dir = os.path.join(os.path.dirname(__file__), 'cjkencodings')
+    with open(os.path.join(dir, name + '.txt'), 'rb') as f:
+        encoded = f.read()
+    with open(os.path.join(dir, name + '-utf8.txt'), 'rb') as f:
+        utf8 = f.read()
+    return encoded, utf8