diff --git a/Lib/test/test_capi/test_unicode.py b/Lib/test/test_capi/test_unicode.py
index 857579f758386f..00807d968a7c43 100644
--- a/Lib/test/test_capi/test_unicode.py
+++ b/Lib/test/test_capi/test_unicode.py
@@ -17,6 +17,287 @@ class Str(str):
 
 class CAPITest(unittest.TestCase):
 
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_new(self):
+        """Test PyUnicode_New()"""
+        from _testcapi import unicode_new as new
+
+        for maxchar in 0, 0x61, 0xa1, 0x4f60, 0x1f600, 0x10ffff:
+            self.assertEqual(new(0, maxchar), '')
+            self.assertEqual(new(5, maxchar), chr(maxchar)*5)
+        self.assertEqual(new(0, 0x110000), '')
+        self.assertRaises(SystemError, new, 5, 0x110000)
+        self.assertRaises(SystemError, new, -1, 0)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_fill(self):
+        """Test PyUnicode_Fill()"""
+        from _testcapi import unicode_fill as fill
+
+        strings = [
+            # all strings have exactly 5 characters
+            'abcde', '\xa1\xa2\xa3\xa4\xa5',
+            '\u4f60\u597d\u4e16\u754c\uff01',
+            '\U0001f600\U0001f601\U0001f602\U0001f603\U0001f604'
+        ]
+        chars = [0x78, 0xa9, 0x20ac, 0x1f638]
+
+        for idx, fill_char in enumerate(chars):
+            # wide -> narrow: exceed maxchar limitation
+            for to in strings[:idx]:
+                self.assertRaises(ValueError, fill, to, 0, 0, fill_char)
+            for to in strings[idx:]:
+                for start in range(7):
+                    for length in range(-1, 7 - start):
+                        filled = max(min(length, 5 - start), 0)
+                        if filled == 5 and to != strings[idx]:
+                            # narrow -> wide
+                            # Tests omitted since this creates invalid strings.
+                            continue
+                        expected = to[:start] + chr(fill_char) * filled + to[start + filled:]
+                        self.assertEqual(fill(to, start, length, fill_char),
+                                        (expected, filled))
+
+        s = strings[0]
+        self.assertRaises(IndexError, fill, s, -1, 0, 0x78)
+        self.assertRaises(ValueError, fill, s, 0, 0, 0x110000)
+        self.assertRaises(SystemError, fill, b'abc', 0, 0, 0x78)
+        self.assertRaises(SystemError, fill, [], 0, 0, 0x78)
+        # CRASHES fill(s, 0, NULL, 0, 0)
+        # CRASHES fill(NULL, 0, 0, 0x78)
+        # TODO: Test PyUnicode_Fill() with non-modifiable unicode.
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_writechar(self):
+        """Test PyUnicode_ReadChar()"""
+        from _testcapi import unicode_writechar as writechar
+
+        strings = [
+            # one string for every kind
+            'abc', '\xa1\xa2\xa3', '\u4f60\u597d\u4e16',
+            '\U0001f600\U0001f601\U0001f602'
+        ]
+        # one character for every kind + out of range code
+        chars = [0x78, 0xa9, 0x20ac, 0x1f638, 0x110000]
+        for i, s in enumerate(strings):
+            for j, c in enumerate(chars):
+                if j <= i:
+                    self.assertEqual(writechar(s, 1, c),
+                                     (s[:1] + chr(c) + s[2:], 0))
+                else:
+                    self.assertRaises(ValueError, writechar, s, 1, c)
+
+        self.assertRaises(IndexError, writechar, 'abc', 3, 0x78)
+        self.assertRaises(IndexError, writechar, 'abc', -1, 0x78)
+        self.assertRaises(TypeError, writechar, b'abc', 0, 0x78)
+        self.assertRaises(TypeError, writechar, [], 0, 0x78)
+        # CRASHES writechar(NULL, 0, 0x78)
+        # TODO: Test PyUnicode_CopyCharacters() with non-modifiable and legacy
+        # unicode.
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_resize(self):
+        """Test PyUnicode_Resize()"""
+        from _testcapi import unicode_resize as resize
+
+        strings = [
+            # all strings have exactly 3 characters
+            'abc', '\xa1\xa2\xa3', '\u4f60\u597d\u4e16',
+            '\U0001f600\U0001f601\U0001f602'
+        ]
+        for s in strings:
+            self.assertEqual(resize(s, 3), (s, 0))
+            self.assertEqual(resize(s, 2), (s[:2], 0))
+            self.assertEqual(resize(s, 4), (s + '\0', 0))
+            self.assertEqual(resize(s, 0), ('', 0))
+        self.assertRaises(SystemError, resize, b'abc', 0)
+        self.assertRaises(SystemError, resize, [], 0)
+        self.assertRaises(SystemError, resize, NULL, 0)
+        # TODO: Test PyUnicode_Resize() with non-modifiable and legacy unicode
+        # and with NULL as the address.
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_append(self):
+        """Test PyUnicode_Append()"""
+        from _testcapi import unicode_append as append
+
+        strings = [
+            'abc', '\xa1\xa2\xa3', '\u4f60\u597d\u4e16',
+            '\U0001f600\U0001f601\U0001f602'
+        ]
+        for left in strings:
+            left = left[::-1]
+            for right in strings:
+                expected = left + right
+                self.assertEqual(append(left, right), expected)
+
+        self.assertRaises(SystemError, append, 'abc', b'abc')
+        self.assertRaises(SystemError, append, b'abc', 'abc')
+        self.assertRaises(SystemError, append, b'abc', b'abc')
+        self.assertRaises(SystemError, append, 'abc', [])
+        self.assertRaises(SystemError, append, [], 'abc')
+        self.assertRaises(SystemError, append, [], [])
+        self.assertRaises(SystemError, append, NULL, 'abc')
+        self.assertRaises(SystemError, append, 'abc', NULL)
+        # TODO: Test PyUnicode_Append() with modifiable unicode
+        # and with NULL as the address.
+        # TODO: Check reference counts.
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_appendanddel(self):
+        """Test PyUnicode_AppendAndDel()"""
+        from _testcapi import unicode_appendanddel as appendanddel
+
+        strings = [
+            'abc', '\xa1\xa2\xa3', '\u4f60\u597d\u4e16',
+            '\U0001f600\U0001f601\U0001f602'
+        ]
+        for left in strings:
+            left = left[::-1]
+            for right in strings:
+                self.assertEqual(appendanddel(left, right), left + right)
+
+        self.assertRaises(SystemError, appendanddel, 'abc', b'abc')
+        self.assertRaises(SystemError, appendanddel, b'abc', 'abc')
+        self.assertRaises(SystemError, appendanddel, b'abc', b'abc')
+        self.assertRaises(SystemError, appendanddel, 'abc', [])
+        self.assertRaises(SystemError, appendanddel, [], 'abc')
+        self.assertRaises(SystemError, appendanddel, [], [])
+        self.assertRaises(SystemError, appendanddel, NULL, 'abc')
+        self.assertRaises(SystemError, appendanddel, 'abc', NULL)
+        # TODO: Test PyUnicode_AppendAndDel() with modifiable unicode
+        # and with NULL as the address.
+        # TODO: Check reference counts.
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_fromstringandsize(self):
+        """Test PyUnicode_FromStringAndSize()"""
+        from _testcapi import unicode_fromstringandsize as fromstringandsize
+
+        self.assertEqual(fromstringandsize(b'abc'), 'abc')
+        self.assertEqual(fromstringandsize(b'abc', 2), 'ab')
+        self.assertEqual(fromstringandsize(b'abc\0def'), 'abc\0def')
+        self.assertEqual(fromstringandsize(b'\xc2\xa1\xc2\xa2'), '\xa1\xa2')
+        self.assertEqual(fromstringandsize(b'\xe4\xbd\xa0'), '\u4f60')
+        self.assertEqual(fromstringandsize(b'\xf0\x9f\x98\x80'), '\U0001f600')
+        self.assertRaises(UnicodeDecodeError, fromstringandsize, b'\xc2\xa1', 1)
+        self.assertRaises(UnicodeDecodeError, fromstringandsize, b'\xa1', 1)
+        self.assertEqual(fromstringandsize(b'', 0), '')
+        self.assertEqual(fromstringandsize(NULL, 0), '')
+
+        self.assertRaises(SystemError, fromstringandsize, b'abc', -1)
+        # TODO: Test PyUnicode_FromStringAndSize(NULL, size) for size != 0
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_fromstring(self):
+        """Test PyUnicode_FromString()"""
+        from _testcapi import unicode_fromstring as fromstring
+
+        self.assertEqual(fromstring(b'abc'), 'abc')
+        self.assertEqual(fromstring(b'\xc2\xa1\xc2\xa2'), '\xa1\xa2')
+        self.assertEqual(fromstring(b'\xe4\xbd\xa0'), '\u4f60')
+        self.assertEqual(fromstring(b'\xf0\x9f\x98\x80'), '\U0001f600')
+        self.assertRaises(UnicodeDecodeError, fromstring, b'\xc2')
+        self.assertRaises(UnicodeDecodeError, fromstring, b'\xa1')
+        self.assertEqual(fromstring(b''), '')
+
+        # CRASHES fromstring(NULL)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_fromkindanddata(self):
+        """Test PyUnicode_FromKindAndData()"""
+        from _testcapi import unicode_fromkindanddata as fromkindanddata
+
+        strings = [
+            'abcde', '\xa1\xa2\xa3\xa4\xa5',
+            '\u4f60\u597d\u4e16\u754c\uff01',
+            '\U0001f600\U0001f601\U0001f602\U0001f603\U0001f604'
+        ]
+        enc1 = 'latin1'
+        for s in strings[:2]:
+            self.assertEqual(fromkindanddata(1, s.encode(enc1)), s)
+        enc2 = 'utf-16le' if sys.byteorder == 'little' else 'utf-16be'
+        for s in strings[:3]:
+            self.assertEqual(fromkindanddata(2, s.encode(enc2)), s)
+        enc4 = 'utf-32le' if sys.byteorder == 'little' else 'utf-32be'
+        for s in strings:
+            self.assertEqual(fromkindanddata(4, s.encode(enc4)), s)
+        self.assertEqual(fromkindanddata(2, '\U0001f600'.encode(enc2)),
+                         '\ud83d\ude00')
+        for kind in 1, 2, 4:
+            self.assertEqual(fromkindanddata(kind, b''), '')
+            self.assertEqual(fromkindanddata(kind, b'\0'*kind), '\0')
+            self.assertEqual(fromkindanddata(kind, NULL, 0), '')
+
+        for kind in -1, 0, 3, 5, 8:
+            self.assertRaises(SystemError, fromkindanddata, kind, b'')
+        self.assertRaises(ValueError, fromkindanddata, 1, b'abc', -1)
+        self.assertRaises(ValueError, fromkindanddata, 1, NULL, -1)
+        # CRASHES fromkindanddata(1, NULL, 1)
+        # CRASHES fromkindanddata(4, b'\xff\xff\xff\xff')
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_substring(self):
+        """Test PyUnicode_Substring()"""
+        from _testcapi import unicode_substring as substring
+
+        strings = [
+            'ab', 'ab\xa1\xa2',
+            'ab\xa1\xa2\u4f60\u597d',
+            'ab\xa1\xa2\u4f60\u597d\U0001f600\U0001f601'
+        ]
+        for s in strings:
+            for start in range(0, len(s) + 2):
+                for end in range(max(start-1, 0), len(s) + 2):
+                    self.assertEqual(substring(s, start, end), s[start:end])
+
+        self.assertRaises(IndexError, substring, 'abc', -1, 0)
+        self.assertRaises(IndexError, substring, 'abc', 0, -1)
+        # CRASHES substring(b'abc', 0, 0)
+        # CRASHES substring([], 0, 0)
+        # CRASHES substring(NULL, 0, 0)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_getlength(self):
+        """Test PyUnicode_GetLength()"""
+        from _testcapi import unicode_getlength as getlength
+
+        for s in ['abc', '\xa1\xa2', '\u4f60\u597d', 'a\U0001f600',
+                  'a\ud800b\udfffc', '\ud834\udd1e']:
+            self.assertEqual(getlength(s), len(s))
+
+        self.assertRaises(TypeError, getlength, b'abc')
+        self.assertRaises(TypeError, getlength, [])
+        # CRASHES getlength(NULL)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_readchar(self):
+        """Test PyUnicode_ReadChar()"""
+        from _testcapi import unicode_readchar as readchar
+
+        for s in ['abc', '\xa1\xa2', '\u4f60\u597d', 'a\U0001f600',
+                  'a\ud800b\udfffc', '\ud834\udd1e']:
+            for i, c in enumerate(s):
+                self.assertEqual(readchar(s, i), ord(c))
+            self.assertRaises(IndexError, readchar, s, len(s))
+            self.assertRaises(IndexError, readchar, s, -1)
+
+        self.assertRaises(TypeError, readchar, b'abc', 0)
+        self.assertRaises(TypeError, readchar, [], 0)
+        # CRASHES readchar(NULL, 0)
+
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
     def test_fromobject(self):
@@ -293,13 +574,70 @@ def check_format(expected, format, *args):
         self.assertRaisesRegex(SystemError, 'invalid format string',
             PyUnicode_FromFormat, b'%+i', c_int(10))
 
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_interninplace(self):
+        """Test PyUnicode_InternInPlace()"""
+        from _testcapi import unicode_interninplace as interninplace
+
+        s = b'abc'.decode()
+        r = interninplace(s)
+        self.assertEqual(r, 'abc')
+
+        # CRASHES interninplace(b'abc')
+        # CRASHES interninplace(NULL)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_internfromstring(self):
+        """Test PyUnicode_InternFromString()"""
+        from _testcapi import unicode_internfromstring as internfromstring
+
+        self.assertEqual(internfromstring(b'abc'), 'abc')
+        self.assertEqual(internfromstring(b'\xf0\x9f\x98\x80'), '\U0001f600')
+        self.assertRaises(UnicodeDecodeError, internfromstring, b'\xc2')
+        self.assertRaises(UnicodeDecodeError, internfromstring, b'\xa1')
+        self.assertEqual(internfromstring(b''), '')
+
+        # CRASHES internfromstring(NULL)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_fromwidechar(self):
+        """Test PyUnicode_FromWideChar()"""
+        from _testcapi import unicode_fromwidechar as fromwidechar
+        from _testcapi import SIZEOF_WCHAR_T
+
+        if SIZEOF_WCHAR_T == 2:
+            encoding = 'utf-16le' if sys.byteorder == 'little' else 'utf-16be'
+        elif SIZEOF_WCHAR_T == 4:
+            encoding = 'utf-32le' if sys.byteorder == 'little' else 'utf-32be'
+
+        for s in '', 'abc', '\xa1\xa2', '\u4f60', '\U0001f600':
+            b = s.encode(encoding)
+            self.assertEqual(fromwidechar(b), s)
+            self.assertEqual(fromwidechar(b + b'\0'*SIZEOF_WCHAR_T, -1), s)
+        for s in '\ud83d', '\ude00':
+            b = s.encode(encoding, 'surrogatepass')
+            self.assertEqual(fromwidechar(b), s)
+            self.assertEqual(fromwidechar(b + b'\0'*SIZEOF_WCHAR_T, -1), s)
+
+        self.assertEqual(fromwidechar('abc'.encode(encoding), 2), 'ab')
+        if SIZEOF_WCHAR_T == 2:
+            self.assertEqual(fromwidechar('a\U0001f600'.encode(encoding), 2), 'a\ud83d')
+
+        self.assertRaises(SystemError, fromwidechar, b'\0'*SIZEOF_WCHAR_T, -2)
+        self.assertEqual(fromwidechar(NULL, 0), '')
+        self.assertRaises(SystemError, fromwidechar, NULL, 1)
+        self.assertRaises(SystemError, fromwidechar, NULL, -1)
+
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
     def test_aswidechar(self):
         """Test PyUnicode_AsWideChar()"""
         from _testcapi import unicode_aswidechar
-        import_helper.import_module('ctypes')
-        from ctypes import c_wchar, sizeof
+        from _testcapi import unicode_aswidechar_null
+        from _testcapi import SIZEOF_WCHAR_T
 
         wchar, size = unicode_aswidechar('abcdef', 2)
         self.assertEqual(size, 2)
@@ -308,6 +646,8 @@ def test_aswidechar(self):
         wchar, size = unicode_aswidechar('abc', 3)
         self.assertEqual(size, 3)
         self.assertEqual(wchar, 'abc')
+        self.assertEqual(unicode_aswidechar_null('abc', 10), 4)
+        self.assertEqual(unicode_aswidechar_null('abc', 0), 4)
 
         wchar, size = unicode_aswidechar('abc', 4)
         self.assertEqual(size, 3)
@@ -320,60 +660,113 @@ def test_aswidechar(self):
         wchar, size = unicode_aswidechar('abc\0def', 20)
         self.assertEqual(size, 7)
         self.assertEqual(wchar, 'abc\0def\0')
+        self.assertEqual(unicode_aswidechar_null('abc\0def', 20), 8)
 
         nonbmp = chr(0x10ffff)
-        if sizeof(c_wchar) == 2:
-            buflen = 3
+        if SIZEOF_WCHAR_T == 2:
             nchar = 2
-        else: # sizeof(c_wchar) == 4
-            buflen = 2
+        else: # SIZEOF_WCHAR_T == 4
             nchar = 1
-        wchar, size = unicode_aswidechar(nonbmp, buflen)
+        wchar, size = unicode_aswidechar(nonbmp, 10)
         self.assertEqual(size, nchar)
         self.assertEqual(wchar, nonbmp + '\0')
+        self.assertEqual(unicode_aswidechar_null(nonbmp, 10), nchar + 1)
+
+        self.assertRaises(TypeError, unicode_aswidechar, b'abc', 10)
+        self.assertRaises(TypeError, unicode_aswidechar, [], 10)
+        self.assertRaises(SystemError, unicode_aswidechar, NULL, 10)
+        self.assertRaises(TypeError, unicode_aswidechar_null, b'abc', 10)
+        self.assertRaises(TypeError, unicode_aswidechar_null, [], 10)
+        self.assertRaises(SystemError, unicode_aswidechar_null, NULL, 10)
 
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
     def test_aswidecharstring(self):
         """Test PyUnicode_AsWideCharString()"""
         from _testcapi import unicode_aswidecharstring
-        import_helper.import_module('ctypes')
-        from ctypes import c_wchar, sizeof
+        from _testcapi import unicode_aswidecharstring_null
+        from _testcapi import SIZEOF_WCHAR_T
 
         wchar, size = unicode_aswidecharstring('abc')
         self.assertEqual(size, 3)
         self.assertEqual(wchar, 'abc\0')
+        self.assertEqual(unicode_aswidecharstring_null('abc'), 'abc')
 
         wchar, size = unicode_aswidecharstring('abc\0def')
         self.assertEqual(size, 7)
         self.assertEqual(wchar, 'abc\0def\0')
+        self.assertRaises(ValueError, unicode_aswidecharstring_null, 'abc\0def')
 
         nonbmp = chr(0x10ffff)
-        if sizeof(c_wchar) == 2:
+        if SIZEOF_WCHAR_T == 2:
             nchar = 2
-        else: # sizeof(c_wchar) == 4
+        else: # SIZEOF_WCHAR_T == 4
             nchar = 1
         wchar, size = unicode_aswidecharstring(nonbmp)
         self.assertEqual(size, nchar)
         self.assertEqual(wchar, nonbmp + '\0')
+        self.assertEqual(unicode_aswidecharstring_null(nonbmp), nonbmp)
+
+        self.assertRaises(TypeError, unicode_aswidecharstring, b'abc')
+        self.assertRaises(TypeError, unicode_aswidecharstring, [])
+        self.assertRaises(SystemError, unicode_aswidecharstring, NULL)
+        self.assertRaises(TypeError, unicode_aswidecharstring_null, b'abc')
+        self.assertRaises(TypeError, unicode_aswidecharstring_null, [])
+        self.assertRaises(SystemError, unicode_aswidecharstring_null, NULL)
 
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
     def test_asucs4(self):
         """Test PyUnicode_AsUCS4()"""
         from _testcapi import unicode_asucs4
+
         for s in ['abc', '\xa1\xa2', '\u4f60\u597d', 'a\U0001f600',
                   'a\ud800b\udfffc', '\ud834\udd1e']:
             l = len(s)
-            self.assertEqual(unicode_asucs4(s, l, True), s+'\0')
-            self.assertEqual(unicode_asucs4(s, l, False), s+'\uffff')
-            self.assertEqual(unicode_asucs4(s, l+1, True), s+'\0\uffff')
-            self.assertEqual(unicode_asucs4(s, l+1, False), s+'\0\uffff')
-            self.assertRaises(SystemError, unicode_asucs4, s, l-1, True)
-            self.assertRaises(SystemError, unicode_asucs4, s, l-2, False)
+            self.assertEqual(unicode_asucs4(s, l, 1), s+'\0')
+            self.assertEqual(unicode_asucs4(s, l, 0), s+'\uffff')
+            self.assertEqual(unicode_asucs4(s, l+1, 1), s+'\0\uffff')
+            self.assertEqual(unicode_asucs4(s, l+1, 0), s+'\0\uffff')
+            self.assertRaises(SystemError, unicode_asucs4, s, l-1, 1)
+            self.assertRaises(SystemError, unicode_asucs4, s, l-2, 0)
+            s = '\0'.join([s, s])
+            self.assertEqual(unicode_asucs4(s, len(s), 1), s+'\0')
+            self.assertEqual(unicode_asucs4(s, len(s), 0), s+'\uffff')
+
+        # CRASHES unicode_asucs4(b'abc', 1, 0)
+        # CRASHES unicode_asucs4(b'abc', 1, 1)
+        # CRASHES unicode_asucs4([], 1, 1)
+        # CRASHES unicode_asucs4(NULL, 1, 0)
+        # CRASHES unicode_asucs4(NULL, 1, 1)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_asucs4copy(self):
+        """Test PyUnicode_AsUCS4Copy()"""
+        from _testcapi import unicode_asucs4copy as asucs4copy
+
+        for s in ['abc', '\xa1\xa2', '\u4f60\u597d', 'a\U0001f600',
+                  'a\ud800b\udfffc', '\ud834\udd1e']:
+            self.assertEqual(asucs4copy(s), s+'\0')
             s = '\0'.join([s, s])
-            self.assertEqual(unicode_asucs4(s, len(s), True), s+'\0')
-            self.assertEqual(unicode_asucs4(s, len(s), False), s+'\uffff')
+            self.assertEqual(asucs4copy(s), s+'\0')
+
+        # CRASHES asucs4copy(b'abc')
+        # CRASHES asucs4copy([])
+        # CRASHES asucs4copy(NULL)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_fromordinal(self):
+        """Test PyUnicode_FromOrdinal()"""
+        from _testcapi import unicode_fromordinal as fromordinal
+
+        self.assertEqual(fromordinal(0x61), 'a')
+        self.assertEqual(fromordinal(0x20ac), '\u20ac')
+        self.assertEqual(fromordinal(0x1f600), '\U0001f600')
+
+        self.assertRaises(ValueError, fromordinal, 0x110000)
+        self.assertRaises(ValueError, fromordinal, -1)
 
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
@@ -381,29 +774,62 @@ def test_asutf8(self):
         """Test PyUnicode_AsUTF8()"""
         from _testcapi import unicode_asutf8
 
-        bmp = '\u0100'
-        bmp2 = '\uffff'
-        nonbmp = chr(0x10ffff)
+        self.assertEqual(unicode_asutf8('abc', 4), b'abc\0')
+        self.assertEqual(unicode_asutf8('абв', 7), b'\xd0\xb0\xd0\xb1\xd0\xb2\0')
+        self.assertEqual(unicode_asutf8('\U0001f600', 5), b'\xf0\x9f\x98\x80\0')
+        self.assertEqual(unicode_asutf8('abc\0def', 8), b'abc\0def\0')
 
-        self.assertEqual(unicode_asutf8(bmp), b'\xc4\x80')
-        self.assertEqual(unicode_asutf8(bmp2), b'\xef\xbf\xbf')
-        self.assertEqual(unicode_asutf8(nonbmp), b'\xf4\x8f\xbf\xbf')
-        self.assertRaises(UnicodeEncodeError, unicode_asutf8, 'a\ud800b\udfffc')
+        self.assertRaises(UnicodeEncodeError, unicode_asutf8, '\ud8ff', 0)
+        self.assertRaises(TypeError, unicode_asutf8, b'abc', 0)
+        self.assertRaises(TypeError, unicode_asutf8, [], 0)
+        # CRASHES unicode_asutf8(NULL, 0)
 
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
     def test_asutf8andsize(self):
         """Test PyUnicode_AsUTF8AndSize()"""
         from _testcapi import unicode_asutf8andsize
+        from _testcapi import unicode_asutf8andsize_null
 
-        bmp = '\u0100'
-        bmp2 = '\uffff'
-        nonbmp = chr(0x10ffff)
+        self.assertEqual(unicode_asutf8andsize('abc', 4), (b'abc\0', 3))
+        self.assertEqual(unicode_asutf8andsize('абв', 7), (b'\xd0\xb0\xd0\xb1\xd0\xb2\0', 6))
+        self.assertEqual(unicode_asutf8andsize('\U0001f600', 5), (b'\xf0\x9f\x98\x80\0', 4))
+        self.assertEqual(unicode_asutf8andsize('abc\0def', 8), (b'abc\0def\0', 7))
+        self.assertEqual(unicode_asutf8andsize_null('abc', 4), b'abc\0')
+        self.assertEqual(unicode_asutf8andsize_null('abc\0def', 8), b'abc\0def\0')
 
-        self.assertEqual(unicode_asutf8andsize(bmp), (b'\xc4\x80', 2))
-        self.assertEqual(unicode_asutf8andsize(bmp2), (b'\xef\xbf\xbf', 3))
-        self.assertEqual(unicode_asutf8andsize(nonbmp), (b'\xf4\x8f\xbf\xbf', 4))
-        self.assertRaises(UnicodeEncodeError, unicode_asutf8andsize, 'a\ud800b\udfffc')
+        self.assertRaises(UnicodeEncodeError, unicode_asutf8andsize, '\ud8ff', 0)
+        self.assertRaises(TypeError, unicode_asutf8andsize, b'abc', 0)
+        self.assertRaises(TypeError, unicode_asutf8andsize, [], 0)
+        # CRASHES unicode_asutf8andsize(NULL, 0)
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_getdefaultencoding(self):
+        """Test PyUnicode_GetDefaultEncoding()"""
+        from _testcapi import unicode_getdefaultencoding as getdefaultencoding
+
+        self.assertEqual(getdefaultencoding(), b'utf-8')
+
+    @support.cpython_only
+    @unittest.skipIf(_testcapi is None, 'need _testcapi module')
+    def test_transform_decimal_and_space(self):
+        """Test _PyUnicode_TransformDecimalAndSpaceToASCII()"""
+        from _testcapi import unicode_transformdecimalandspacetoascii as transform_decimal
+
+        self.assertEqual(transform_decimal('123'),
+                         '123')
+        self.assertEqual(transform_decimal('\u0663.\u0661\u0664'),
+                         '3.14')
+        self.assertEqual(transform_decimal("\N{EM SPACE}3.14\N{EN SPACE}"),
+                         " 3.14 ")
+        self.assertEqual(transform_decimal('12\u20ac3'),
+                         '12?')
+        self.assertEqual(transform_decimal(''), '')
+
+        self.assertRaises(SystemError, transform_decimal, b'123')
+        self.assertRaises(SystemError, transform_decimal, [])
+        # CRASHES transform_decimal(NULL)
 
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
@@ -858,6 +1284,7 @@ def test_copycharacters(self):
         from _testcapi import unicode_copycharacters
 
         strings = [
+            # all strings have exactly 5 characters
             'abcde', '\xa1\xa2\xa3\xa4\xa5',
             '\u4f60\u597d\u4e16\u754c\uff01',
             '\U0001f600\U0001f601\U0001f602\U0001f603\U0001f604'
@@ -894,6 +1321,10 @@ def test_copycharacters(self):
         self.assertRaises(SystemError, unicode_copycharacters, s, 1, s, 0, 5)
         self.assertRaises(SystemError, unicode_copycharacters, s, 0, s, 0, -1)
         self.assertRaises(SystemError, unicode_copycharacters, s, 0, b'', 0, 0)
+        self.assertRaises(SystemError, unicode_copycharacters, s, 0, [], 0, 0)
+        # CRASHES unicode_copycharacters(s, 0, NULL, 0, 0)
+        # TODO: Test PyUnicode_CopyCharacters() with non-unicode and
+        # non-modifiable unicode as "to".
 
     @support.cpython_only
     @unittest.skipIf(_testcapi is None, 'need _testcapi module')
diff --git a/Modules/_testcapi/unicode.c b/Modules/_testcapi/unicode.c
index 2d23993ce420b3..7dd3b9c0c03e50 100644
--- a/Modules/_testcapi/unicode.c
+++ b/Modules/_testcapi/unicode.c
@@ -102,6 +102,278 @@ test_widechar(PyObject *self, PyObject *Py_UNUSED(ignored))
 
 #define NULLABLE(x) do { if (x == Py_None) x = NULL; } while (0);
 
+static PyObject *
+unicode_copy(PyObject *unicode)
+{
+    PyObject *copy;
+
+    if (!unicode) {
+        return NULL;
+    }
+    if (!PyUnicode_Check(unicode)) {
+        Py_INCREF(unicode);
+        return unicode;
+    }
+
+    copy = PyUnicode_New(PyUnicode_GET_LENGTH(unicode),
+                         PyUnicode_MAX_CHAR_VALUE(unicode));
+    if (!copy) {
+        return NULL;
+    }
+    if (PyUnicode_CopyCharacters(copy, 0, unicode,
+                                 0, PyUnicode_GET_LENGTH(unicode)) < 0)
+    {
+        Py_DECREF(copy);
+        return NULL;
+    }
+    return copy;
+}
+
+/* Test PyUnicode_New() */
+static PyObject *
+unicode_new(PyObject *self, PyObject *args)
+{
+    Py_ssize_t size;
+    unsigned int maxchar;
+    PyObject *result;
+
+    if (!PyArg_ParseTuple(args, "nI", &size, &maxchar)) {
+        return NULL;
+    }
+
+    result = PyUnicode_New(size, (Py_UCS4)maxchar);
+    if (!result) {
+        return NULL;
+    }
+    if (size > 0 && maxchar <= 0x10ffff &&
+        PyUnicode_Fill(result, 0, size, (Py_UCS4)maxchar) < 0)
+    {
+        Py_DECREF(result);
+        return NULL;
+    }
+    return result;
+}
+
+/* Test PyUnicode_Fill() */
+static PyObject *
+unicode_fill(PyObject *self, PyObject *args)
+{
+    PyObject *to, *to_copy;
+    Py_ssize_t start, length, filled;
+    unsigned int fill_char;
+
+    if (!PyArg_ParseTuple(args, "OnnI", &to, &start, &length, &fill_char)) {
+        return NULL;
+    }
+
+    NULLABLE(to);
+    if (!(to_copy = unicode_copy(to)) && to) {
+        return NULL;
+    }
+
+    filled = PyUnicode_Fill(to_copy, start, length, (Py_UCS4)fill_char);
+    if (filled == -1 && PyErr_Occurred()) {
+        Py_DECREF(to_copy);
+        return NULL;
+    }
+    return Py_BuildValue("(Nn)", to_copy, filled);
+}
+
+/* Test PyUnicode_WriteChar() */
+static PyObject *
+unicode_writechar(PyObject *self, PyObject *args)
+{
+    PyObject *to, *to_copy;
+    Py_ssize_t index;
+    unsigned int character;
+    int result;
+
+    if (!PyArg_ParseTuple(args, "OnI", &to, &index, &character)) {
+        return NULL;
+    }
+
+    NULLABLE(to);
+    if (!(to_copy = unicode_copy(to)) && to) {
+        return NULL;
+    }
+
+    result = PyUnicode_WriteChar(to_copy, index, (Py_UCS4)character);
+    if (result == -1 && PyErr_Occurred()) {
+        Py_DECREF(to_copy);
+        return NULL;
+    }
+    return Py_BuildValue("(Ni)", to_copy, result);
+}
+
+/* Test PyUnicode_Resize() */
+static PyObject *
+unicode_resize(PyObject *self, PyObject *args)
+{
+    PyObject *obj, *copy;
+    Py_ssize_t length;
+    int result;
+
+    if (!PyArg_ParseTuple(args, "On", &obj, &length)) {
+        return NULL;
+    }
+
+    NULLABLE(obj);
+    if (!(copy = unicode_copy(obj)) && obj) {
+        return NULL;
+    }
+    result = PyUnicode_Resize(&copy, length);
+    if (result == -1 && PyErr_Occurred()) {
+        Py_XDECREF(copy);
+        return NULL;
+    }
+    if (obj && PyUnicode_Check(obj) && length > PyUnicode_GET_LENGTH(obj)) {
+        if (PyUnicode_Fill(copy, PyUnicode_GET_LENGTH(obj), length, 0U) < 0) {
+            Py_DECREF(copy);
+            return NULL;
+        }
+    }
+    return Py_BuildValue("(Ni)", copy, result);
+}
+
+/* Test PyUnicode_Append() */
+static PyObject *
+unicode_append(PyObject *self, PyObject *args)
+{
+    PyObject *left, *right, *left_copy;
+
+    if (!PyArg_ParseTuple(args, "OO", &left, &right))
+        return NULL;
+
+    NULLABLE(left);
+    NULLABLE(right);
+    if (!(left_copy = unicode_copy(left)) && left) {
+        return NULL;
+    }
+    PyUnicode_Append(&left_copy, right);
+    return left_copy;
+}
+
+/* Test PyUnicode_AppendAndDel() */
+static PyObject *
+unicode_appendanddel(PyObject *self, PyObject *args)
+{
+    PyObject *left, *right, *left_copy;
+
+    if (!PyArg_ParseTuple(args, "OO", &left, &right))
+        return NULL;
+
+    NULLABLE(left);
+    NULLABLE(right);
+    if (!(left_copy = unicode_copy(left)) && left) {
+        return NULL;
+    }
+    Py_XINCREF(right);
+    PyUnicode_AppendAndDel(&left_copy, right);
+    return left_copy;
+}
+
+/* Test PyUnicode_FromStringAndSize() */
+static PyObject *
+unicode_fromstringandsize(PyObject *self, PyObject *args)
+{
+    const char *s;
+    Py_ssize_t bsize;
+    Py_ssize_t size = -100;
+
+    if (!PyArg_ParseTuple(args, "z#|n", &s, &bsize, &size)) {
+        return NULL;
+    }
+
+    if (size == -100) {
+        size = bsize;
+    }
+    return PyUnicode_FromStringAndSize(s, size);
+}
+
+/* Test PyUnicode_FromString() */
+static PyObject *
+unicode_fromstring(PyObject *self, PyObject *arg)
+{
+    const char *s;
+    Py_ssize_t size;
+
+    if (!PyArg_Parse(arg, "z#", &s, &size)) {
+        return NULL;
+    }
+    return PyUnicode_FromString(s);
+}
+
+/* Test PyUnicode_FromKindAndData() */
+static PyObject *
+unicode_fromkindanddata(PyObject *self, PyObject *args)
+{
+    int kind;
+    void *buffer;
+    Py_ssize_t bsize;
+    Py_ssize_t size = -100;
+
+    if (!PyArg_ParseTuple(args, "iz#|n", &kind, &buffer, &bsize, &size)) {
+        return NULL;
+    }
+
+    if (size == -100) {
+        size = bsize;
+    }
+    if (kind && size % kind) {
+        PyErr_SetString(PyExc_AssertionError,
+                        "invalid size in unicode_fromkindanddata()");
+        return NULL;
+    }
+    return PyUnicode_FromKindAndData(kind, buffer, kind ? size / kind : 0);
+}
+
+/* Test PyUnicode_Substring() */
+static PyObject *
+unicode_substring(PyObject *self, PyObject *args)
+{
+    PyObject *str;
+    Py_ssize_t start, end;
+
+    if (!PyArg_ParseTuple(args, "Onn", &str, &start, &end)) {
+        return NULL;
+    }
+
+    NULLABLE(str);
+    return PyUnicode_Substring(str, start, end);
+}
+
+/* Test PyUnicode_GetLength() */
+static PyObject *
+unicode_getlength(PyObject *self, PyObject *arg)
+{
+    Py_ssize_t result;
+
+    NULLABLE(arg);
+    result = PyUnicode_GetLength(arg);
+    if (result == -1)
+        return NULL;
+    return PyLong_FromSsize_t(result);
+}
+
+/* Test PyUnicode_ReadChar() */
+static PyObject *
+unicode_readchar(PyObject *self, PyObject *args)
+{
+    PyObject *unicode;
+    Py_ssize_t index;
+    Py_UCS4 result;
+
+    if (!PyArg_ParseTuple(args, "On", &unicode, &index)) {
+        return NULL;
+    }
+
+    NULLABLE(unicode);
+    result = PyUnicode_ReadChar(unicode, index);
+    if (result == (Py_UCS4)-1)
+        return NULL;
+    return PyLong_FromUnsignedLong(result);
+}
+
 /* Test PyUnicode_FromObject() */
 static PyObject *
 unicode_fromobject(PyObject *self, PyObject *arg)
@@ -110,6 +382,51 @@ unicode_fromobject(PyObject *self, PyObject *arg)
     return PyUnicode_FromObject(arg);
 }
 
+/* Test PyUnicode_InternInPlace() */
+static PyObject *
+unicode_interninplace(PyObject *self, PyObject *arg)
+{
+    NULLABLE(arg);
+    Py_XINCREF(arg);
+    PyUnicode_InternInPlace(&arg);
+    return arg;
+}
+
+/* Test PyUnicode_InternFromString() */
+static PyObject *
+unicode_internfromstring(PyObject *self, PyObject *arg)
+{
+    const char *s;
+    Py_ssize_t size;
+
+    if (!PyArg_Parse(arg, "z#", &s, &size)) {
+        return NULL;
+    }
+    return PyUnicode_InternFromString(s);
+}
+
+/* Test PyUnicode_FromWideChar() */
+static PyObject *
+unicode_fromwidechar(PyObject *self, PyObject *args)
+{
+    const char *s;
+    Py_ssize_t bsize;
+    Py_ssize_t size = -100;
+
+    if (!PyArg_ParseTuple(args, "z#|n", &s, &bsize, &size)) {
+        return NULL;
+    }
+    if (size == -100) {
+        if (bsize % SIZEOF_WCHAR_T) {
+            PyErr_SetString(PyExc_AssertionError,
+                            "invalid size in unicode_fromwidechar()");
+            return NULL;
+        }
+        size = bsize / SIZEOF_WCHAR_T;
+    }
+    return PyUnicode_FromWideChar((const wchar_t *)s, size);
+}
+
 /* Test PyUnicode_AsWideChar() */
 static PyObject *
 unicode_aswidechar(PyObject *self, PyObject *args)
@@ -118,8 +435,9 @@ unicode_aswidechar(PyObject *self, PyObject *args)
     Py_ssize_t buflen, size;
     wchar_t *buffer;
 
-    if (!PyArg_ParseTuple(args, "Un", &unicode, &buflen))
+    if (!PyArg_ParseTuple(args, "On", &unicode, &buflen))
         return NULL;
+    NULLABLE(unicode);
     buffer = PyMem_New(wchar_t, buflen);
     if (buffer == NULL)
         return PyErr_NoMemory();
@@ -142,17 +460,35 @@ unicode_aswidechar(PyObject *self, PyObject *args)
     return Py_BuildValue("(Nn)", result, size);
 }
 
+/* Test PyUnicode_AsWideCharString() with NULL as buffer */
+static PyObject *
+unicode_aswidechar_null(PyObject *self, PyObject *args)
+{
+    PyObject *unicode;
+    Py_ssize_t buflen, size;
+
+    if (!PyArg_ParseTuple(args, "On", &unicode, &buflen))
+        return NULL;
+    NULLABLE(unicode);
+    size = PyUnicode_AsWideChar(unicode, NULL, buflen);
+    if (size == -1) {
+        return NULL;
+    }
+    return PyLong_FromSsize_t(size);
+}
+
 /* Test PyUnicode_AsWideCharString() */
 static PyObject *
 unicode_aswidecharstring(PyObject *self, PyObject *args)
 {
     PyObject *unicode, *result;
-    Py_ssize_t size;
+    Py_ssize_t size = 100;
     wchar_t *buffer;
 
-    if (!PyArg_ParseTuple(args, "U", &unicode))
+    if (!PyArg_ParseTuple(args, "O", &unicode))
         return NULL;
 
+    NULLABLE(unicode);
     buffer = PyUnicode_AsWideCharString(unicode, &size);
     if (buffer == NULL)
         return NULL;
@@ -164,6 +500,28 @@ unicode_aswidecharstring(PyObject *self, PyObject *args)
     return Py_BuildValue("(Nn)", result, size);
 }
 
+/* Test PyUnicode_AsWideCharString() with NULL as the size address */
+static PyObject *
+unicode_aswidecharstring_null(PyObject *self, PyObject *args)
+{
+    PyObject *unicode, *result;
+    wchar_t *buffer;
+
+    if (!PyArg_ParseTuple(args, "O", &unicode))
+        return NULL;
+
+    NULLABLE(unicode);
+    buffer = PyUnicode_AsWideCharString(unicode, NULL);
+    if (buffer == NULL)
+        return NULL;
+
+    result = PyUnicode_FromWideChar(buffer, -1);
+    PyMem_Free(buffer);
+    if (result == NULL)
+        return NULL;
+    return result;
+}
+
 /* Test PyUnicode_AsUCS4() */
 static PyObject *
 unicode_asucs4(PyObject *self, PyObject *args)
@@ -173,10 +531,11 @@ unicode_asucs4(PyObject *self, PyObject *args)
     int copy_null;
     Py_ssize_t str_len, buf_len;
 
-    if (!PyArg_ParseTuple(args, "Unp:unicode_asucs4", &unicode, &str_len, &copy_null)) {
+    if (!PyArg_ParseTuple(args, "Onp:unicode_asucs4", &unicode, &str_len, &copy_null)) {
         return NULL;
     }
 
+    NULLABLE(unicode);
     buf_len = str_len + 1;
     buffer = PyMem_NEW(Py_UCS4, buf_len);
     if (buffer == NULL) {
@@ -195,48 +554,117 @@ unicode_asucs4(PyObject *self, PyObject *args)
     return result;
 }
 
-/* Test PyUnicode_AsUTF8() */
+/* Test PyUnicode_AsUCS4Copy() */
 static PyObject *
-unicode_asutf8(PyObject *self, PyObject *args)
+unicode_asucs4copy(PyObject *self, PyObject *args)
 {
     PyObject *unicode;
-    const char *buffer;
+    Py_UCS4 *buffer;
+    PyObject *result;
 
-    if (!PyArg_ParseTuple(args, "U", &unicode)) {
+    if (!PyArg_ParseTuple(args, "O", &unicode)) {
         return NULL;
     }
 
-    buffer = PyUnicode_AsUTF8(unicode);
+    NULLABLE(unicode);
+    buffer = PyUnicode_AsUCS4Copy(unicode);
     if (buffer == NULL) {
         return NULL;
     }
+    result = PyUnicode_FromKindAndData(PyUnicode_4BYTE_KIND,
+                                       buffer,
+                                       PyUnicode_GET_LENGTH(unicode) + 1);
+    PyMem_FREE(buffer);
+    return result;
+}
+
+/* Test PyUnicode_FromOrdinal() */
+static PyObject *
+unicode_fromordinal(PyObject *self, PyObject *args)
+{
+    int ordinal;
+
+    if (!PyArg_ParseTuple(args, "i", &ordinal))
+        return NULL;
 
-    return PyBytes_FromString(buffer);
+    return PyUnicode_FromOrdinal(ordinal);
+}
+
+/* Test PyUnicode_AsUTF8() */
+static PyObject *
+unicode_asutf8(PyObject *self, PyObject *args)
+{
+    PyObject *unicode;
+    Py_ssize_t buflen;
+    const char *s;
+
+    if (!PyArg_ParseTuple(args, "On", &unicode, &buflen))
+        return NULL;
+
+    NULLABLE(unicode);
+    s = PyUnicode_AsUTF8(unicode);
+    if (s == NULL)
+        return NULL;
+
+    return PyBytes_FromStringAndSize(s, buflen);
 }
 
 /* Test PyUnicode_AsUTF8AndSize() */
 static PyObject *
 unicode_asutf8andsize(PyObject *self, PyObject *args)
 {
-    PyObject *unicode, *result;
-    const char *buffer;
-    Py_ssize_t utf8_len;
+    PyObject *unicode;
+    Py_ssize_t buflen;
+    const char *s;
+    Py_ssize_t size = -100;
 
-    if(!PyArg_ParseTuple(args, "U", &unicode)) {
+    if (!PyArg_ParseTuple(args, "On", &unicode, &buflen))
         return NULL;
-    }
 
-    buffer = PyUnicode_AsUTF8AndSize(unicode, &utf8_len);
-    if (buffer == NULL) {
+    NULLABLE(unicode);
+    s = PyUnicode_AsUTF8AndSize(unicode, &size);
+    if (s == NULL)
         return NULL;
-    }
 
-    result = PyBytes_FromString(buffer);
-    if (result == NULL) {
+    return Py_BuildValue("(y#n)", s, buflen, size);
+}
+
+/* Test PyUnicode_AsUTF8AndSize() with NULL as the size address */
+static PyObject *
+unicode_asutf8andsize_null(PyObject *self, PyObject *args)
+{
+    PyObject *unicode;
+    Py_ssize_t buflen;
+    const char *s;
+
+    if (!PyArg_ParseTuple(args, "On", &unicode, &buflen))
         return NULL;
-    }
 
-    return Py_BuildValue("(Nn)", result, utf8_len);
+    NULLABLE(unicode);
+    s = PyUnicode_AsUTF8AndSize(unicode, NULL);
+    if (s == NULL)
+        return NULL;
+
+    return PyBytes_FromStringAndSize(s, buflen);
+}
+
+/* Test PyUnicode_GetDefaultEncoding() */
+static PyObject *
+unicode_getdefaultencoding(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    const char *s = PyUnicode_GetDefaultEncoding();
+    if (s == NULL)
+        return NULL;
+
+    return PyBytes_FromString(s);
+}
+
+/* Test _PyUnicode_TransformDecimalAndSpaceToASCII() */
+static PyObject *
+unicode_transformdecimalandspacetoascii(PyObject *self, PyObject *arg)
+{
+    NULLABLE(arg);
+    return _PyUnicode_TransformDecimalAndSpaceToASCII(arg);
 }
 
 /* Test PyUnicode_DecodeUTF8() */
@@ -470,11 +898,11 @@ unicode_findchar(PyObject *self, PyObject *args)
     Py_ssize_t result;
     Py_ssize_t start, end;
 
-    if (!PyArg_ParseTuple(args, "UInni:unicode_findchar", &str, &ch,
+    if (!PyArg_ParseTuple(args, "OInni:unicode_findchar", &str, &ch,
                           &start, &end, &direction)) {
         return NULL;
     }
-
+    NULLABLE(str);
     result = PyUnicode_FindChar(str, (Py_UCS4)ch, start, end, direction);
     if (result == -2)
         return NULL;
@@ -612,11 +1040,12 @@ unicode_copycharacters(PyObject *self, PyObject *args)
     PyObject *from, *to, *to_copy;
     Py_ssize_t from_start, to_start, how_many, copied;
 
-    if (!PyArg_ParseTuple(args, "UnOnn:unicode_copycharacters", &to, &to_start,
+    if (!PyArg_ParseTuple(args, "UnOnn", &to, &to_start,
                           &from, &from_start, &how_many)) {
         return NULL;
     }
 
+    NULLABLE(from);
     if (!(to_copy = PyUnicode_New(PyUnicode_GET_LENGTH(to),
                                   PyUnicode_MAX_CHAR_VALUE(to)))) {
         return NULL;
@@ -626,8 +1055,9 @@ unicode_copycharacters(PyObject *self, PyObject *args)
         return NULL;
     }
 
-    if ((copied = PyUnicode_CopyCharacters(to_copy, to_start, from,
-                                           from_start, how_many)) < 0) {
+    copied = PyUnicode_CopyCharacters(to_copy, to_start, from,
+                                      from_start, how_many);
+    if (copied == -1 && PyErr_Occurred()) {
         Py_DECREF(to_copy);
         return NULL;
     }
@@ -1053,14 +1483,36 @@ static PyMethodDef TestMethods[] = {
      test_unicode_compare_with_ascii,                            METH_NOARGS},
     {"test_string_from_format",  test_string_from_format,        METH_NOARGS},
     {"test_widechar",            test_widechar,                  METH_NOARGS},
+    {"unicode_new",              unicode_new,                    METH_VARARGS},
+    {"unicode_fill",             unicode_fill,                   METH_VARARGS},
+    {"unicode_writechar",        unicode_writechar,              METH_VARARGS},
+    {"unicode_resize",           unicode_resize,                 METH_VARARGS},
+    {"unicode_append",           unicode_append,                 METH_VARARGS},
+    {"unicode_appendanddel",     unicode_appendanddel,           METH_VARARGS},
+    {"unicode_fromstringandsize",unicode_fromstringandsize,      METH_VARARGS},
+    {"unicode_fromstring",       unicode_fromstring,             METH_O},
+    {"unicode_fromkindanddata",  unicode_fromkindanddata,        METH_VARARGS},
+    {"unicode_substring",        unicode_substring,              METH_VARARGS},
+    {"unicode_getlength",        unicode_getlength,              METH_O},
+    {"unicode_readchar",         unicode_readchar,               METH_VARARGS},
     {"unicode_fromobject",       unicode_fromobject,             METH_O},
+    {"unicode_interninplace",    unicode_interninplace,          METH_O},
+    {"unicode_internfromstring", unicode_internfromstring,       METH_O},
+    {"unicode_fromwidechar",     unicode_fromwidechar,           METH_VARARGS},
     {"unicode_aswidechar",       unicode_aswidechar,             METH_VARARGS},
+    {"unicode_aswidechar_null",  unicode_aswidechar_null,        METH_VARARGS},
     {"unicode_aswidecharstring", unicode_aswidecharstring,       METH_VARARGS},
+    {"unicode_aswidecharstring_null",unicode_aswidecharstring_null,METH_VARARGS},
     {"unicode_asucs4",           unicode_asucs4,                 METH_VARARGS},
+    {"unicode_asucs4copy",       unicode_asucs4copy,             METH_VARARGS},
+    {"unicode_fromordinal",      unicode_fromordinal,            METH_VARARGS},
     {"unicode_asutf8",           unicode_asutf8,                 METH_VARARGS},
     {"unicode_asutf8andsize",    unicode_asutf8andsize,          METH_VARARGS},
+    {"unicode_asutf8andsize_null",unicode_asutf8andsize_null,    METH_VARARGS},
     {"unicode_decodeutf8",       unicode_decodeutf8,             METH_VARARGS},
     {"unicode_decodeutf8stateful",unicode_decodeutf8stateful,    METH_VARARGS},
+    {"unicode_getdefaultencoding",unicode_getdefaultencoding,    METH_NOARGS},
+    {"unicode_transformdecimalandspacetoascii", unicode_transformdecimalandspacetoascii, METH_O},
     {"unicode_concat",           unicode_concat,                 METH_VARARGS},
     {"unicode_splitlines",       unicode_splitlines,             METH_VARARGS},
     {"unicode_split",            unicode_split,                  METH_VARARGS},
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 38f4758e6575d8..ae70a33eb4d1ed 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -4247,6 +4247,7 @@ PyInit__testcapi(void)
     PyModule_AddObject(m, "ULLONG_MAX", PyLong_FromUnsignedLongLong(ULLONG_MAX));
     PyModule_AddObject(m, "PY_SSIZE_T_MAX", PyLong_FromSsize_t(PY_SSIZE_T_MAX));
     PyModule_AddObject(m, "PY_SSIZE_T_MIN", PyLong_FromSsize_t(PY_SSIZE_T_MIN));
+    PyModule_AddObject(m, "SIZEOF_WCHAR_T", PyLong_FromSsize_t(sizeof(wchar_t)));
     PyModule_AddObject(m, "SIZEOF_TIME_T", PyLong_FromSsize_t(sizeof(time_t)));
     PyModule_AddObject(m, "Py_Version", PyLong_FromUnsignedLong(Py_Version));
     Py_INCREF(&PyInstanceMethod_Type);