diff --git a/Lib/test/test_genericpath.py b/Lib/test/test_genericpath.py
index ec722f3c1e9..614f887dad0 100644
--- a/Lib/test/test_genericpath.py
+++ b/Lib/test/test_genericpath.py
@@ -1,38 +1,87 @@
+"""
+Tests common to genericpath, macpath, ntpath and posixpath
+"""
+
 import unittest
 from test import support
 import os
 import genericpath
 
-class AllCommonTest(unittest.TestCase):
+
+def safe_rmdir(dirname):
+    try:
+        os.rmdir(dirname)
+    except OSError:
+        pass
+
+
+class GenericTest(unittest.TestCase):
+    # The path module to be tested
+    pathmodule = genericpath
+    common_attributes = ['commonprefix', 'getsize', 'getatime', 'getctime',
+                         'getmtime', 'exists', 'isdir', 'isfile']
+    attributes = []
+
+    def test_no_argument(self):
+        for attr in self.common_attributes + self.attributes:
+            with self.assertRaises(TypeError):
+                getattr(self.pathmodule, attr)()
+                raise self.fail("{}.{}() did not raise a TypeError"
+                                .format(self.pathmodule.__name__, attr))
 
     def test_commonprefix(self):
+        commonprefix = self.pathmodule.commonprefix
         self.assertEqual(
-            genericpath.commonprefix([]),
+            commonprefix([]),
             ""
         )
         self.assertEqual(
-            genericpath.commonprefix(["/home/swenson/spam", "/home/swen/spam"]),
+            commonprefix(["/home/swenson/spam", "/home/swen/spam"]),
             "/home/swen"
         )
         self.assertEqual(
-            genericpath.commonprefix(["/home/swen/spam", "/home/swen/eggs"]),
+            commonprefix(["/home/swen/spam", "/home/swen/eggs"]),
             "/home/swen/"
         )
         self.assertEqual(
-            genericpath.commonprefix(["/home/swen/spam", "/home/swen/spam"]),
+            commonprefix(["/home/swen/spam", "/home/swen/spam"]),
             "/home/swen/spam"
         )
 
+        self.assertEqual(
+            commonprefix([b"/home/swenson/spam", b"/home/swen/spam"]),
+            b"/home/swen"
+        )
+        self.assertEqual(
+            commonprefix([b"/home/swen/spam", b"/home/swen/eggs"]),
+            b"/home/swen/"
+        )
+        self.assertEqual(
+            commonprefix([b"/home/swen/spam", b"/home/swen/spam"]),
+            b"/home/swen/spam"
+        )
+
+        testlist = ['', 'abc', 'Xbcd', 'Xb', 'XY', 'abcd',
+                    'aXc', 'abd', 'ab', 'aX', 'abcX']
+        for s1 in testlist:
+            for s2 in testlist:
+                p = commonprefix([s1, s2])
+                self.assertTrue(s1.startswith(p))
+                self.assertTrue(s2.startswith(p))
+                if s1 != s2:
+                    n = len(p)
+                    self.assertNotEqual(s1[n:n+1], s2[n:n+1])
+
     def test_getsize(self):
         f = open(support.TESTFN, "wb")
         try:
             f.write(b"foo")
             f.close()
-            self.assertEqual(genericpath.getsize(support.TESTFN), 3)
+            self.assertEqual(self.pathmodule.getsize(support.TESTFN), 3)
         finally:
             if not f.closed:
                 f.close()
-            os.remove(support.TESTFN)
+            support.unlink(support.TESTFN)
 
     def test_time(self):
         f = open(support.TESTFN, "wb")
@@ -48,134 +97,177 @@ class AllCommonTest(unittest.TestCase):
             self.assertEqual(d, b"foobar")
 
             self.assertLessEqual(
-                genericpath.getctime(support.TESTFN),
-                genericpath.getmtime(support.TESTFN)
+                self.pathmodule.getctime(support.TESTFN),
+                self.pathmodule.getmtime(support.TESTFN)
             )
         finally:
             if not f.closed:
                 f.close()
-            os.remove(support.TESTFN)
+            support.unlink(support.TESTFN)
 
     def test_exists(self):
-        self.assertIs(genericpath.exists(support.TESTFN), False)
+        self.assertIs(self.pathmodule.exists(support.TESTFN), False)
         f = open(support.TESTFN, "wb")
         try:
             f.write(b"foo")
             f.close()
-            self.assertIs(genericpath.exists(support.TESTFN), True)
+            self.assertIs(self.pathmodule.exists(support.TESTFN), True)
+            if not self.pathmodule == genericpath:
+                self.assertIs(self.pathmodule.lexists(support.TESTFN),
+                              True)
         finally:
             if not f.close():
                 f.close()
-            try:
-                os.remove(support.TESTFN)
-            except os.error:
-                pass
-
-        self.assertRaises(TypeError, genericpath.exists)
+            support.unlink(support.TESTFN)
 
     def test_isdir(self):
-        self.assertIs(genericpath.isdir(support.TESTFN), False)
+        self.assertIs(self.pathmodule.isdir(support.TESTFN), False)
         f = open(support.TESTFN, "wb")
         try:
             f.write(b"foo")
             f.close()
-            self.assertIs(genericpath.isdir(support.TESTFN), False)
+            self.assertIs(self.pathmodule.isdir(support.TESTFN), False)
             os.remove(support.TESTFN)
             os.mkdir(support.TESTFN)
-            self.assertIs(genericpath.isdir(support.TESTFN), True)
+            self.assertIs(self.pathmodule.isdir(support.TESTFN), True)
             os.rmdir(support.TESTFN)
         finally:
             if not f.close():
                 f.close()
-            try:
-                os.remove(support.TESTFN)
-            except os.error:
-                pass
-            try:
-                os.rmdir(support.TESTFN)
-            except os.error:
-                pass
-
-        self.assertRaises(TypeError, genericpath.isdir)
+            support.unlink(support.TESTFN)
+            safe_rmdir(support.TESTFN)
 
     def test_isfile(self):
-        self.assertIs(genericpath.isfile(support.TESTFN), False)
+        self.assertIs(self.pathmodule.isfile(support.TESTFN), False)
         f = open(support.TESTFN, "wb")
         try:
             f.write(b"foo")
             f.close()
-            self.assertIs(genericpath.isfile(support.TESTFN), True)
+            self.assertIs(self.pathmodule.isfile(support.TESTFN), True)
             os.remove(support.TESTFN)
             os.mkdir(support.TESTFN)
-            self.assertIs(genericpath.isfile(support.TESTFN), False)
+            self.assertIs(self.pathmodule.isfile(support.TESTFN), False)
             os.rmdir(support.TESTFN)
         finally:
             if not f.close():
                 f.close()
-            try:
-                os.remove(support.TESTFN)
-            except os.error:
-                pass
-            try:
-                os.rmdir(support.TESTFN)
-            except os.error:
-                pass
+            support.unlink(support.TESTFN)
+            safe_rmdir(support.TESTFN)
 
-        self.assertRaises(TypeError, genericpath.isdir)
 
-        def test_samefile(self):
-            f = open(support.TESTFN + "1", "wb")
-            try:
-                f.write(b"foo")
-                f.close()
-                self.assertIs(
-                    genericpath.samefile(
-                        support.TESTFN + "1",
-                        support.TESTFN + "1"
-                    ),
-                    True
-                )
-                # If we don't have links, assume that os.stat doesn't return resonable
-                # inode information and thus, that samefile() doesn't work
-                if hasattr(os, "symlink"):
-                    os.symlink(
-                        support.TESTFN + "1",
-                        support.TESTFN + "2"
-                    )
-                    self.assertIs(
-                        genericpath.samefile(
-                            support.TESTFN + "1",
-                            support.TESTFN + "2"
-                        ),
-                        True
-                    )
-                    os.remove(support.TESTFN + "2")
-                    f = open(support.TESTFN + "2", "wb")
-                    f.write(b"bar")
-                    f.close()
-                    self.assertIs(
-                        genericpath.samefile(
-                            support.TESTFN + "1",
-                            support.TESTFN + "2"
-                        ),
-                        False
-                    )
-            finally:
-                if not f.close():
-                    f.close()
-                try:
-                    os.remove(support.TESTFN + "1")
-                except os.error:
-                    pass
-                try:
-                    os.remove(support.TESTFN + "2")
-                except os.error:
-                    pass
+class CommonTest(GenericTest):
+    # The path module to be tested
+    pathmodule = None
+    common_attributes = GenericTest.common_attributes + [
+        # Properties
+        'curdir', 'pardir', 'extsep', 'sep',
+        'pathsep', 'defpath', 'altsep', 'devnull',
+        # Methods
+        'normcase', 'splitdrive', 'expandvars', 'normpath', 'abspath',
+        'join', 'split', 'splitext', 'isabs', 'basename', 'dirname',
+        'lexists', 'islink', 'ismount', 'expanduser', 'normpath', 'realpath',
+    ]
+
+    def test_normcase(self):
+        # Check that normcase() is idempotent
+        p = "FoO/./BaR"
+        p = self.pathmodule.normcase(p)
+        self.assertEqual(p, self.pathmodule.normcase(p))
+
+        p = b"FoO/./BaR"
+        p = self.pathmodule.normcase(p)
+        self.assertEqual(p, self.pathmodule.normcase(p))
+
+    def test_splitdrive(self):
+        # splitdrive for non-NT paths
+        splitdrive = self.pathmodule.splitdrive
+        self.assertEqual(splitdrive("/foo/bar"), ("", "/foo/bar"))
+        self.assertEqual(splitdrive("foo:bar"), ("", "foo:bar"))
+        self.assertEqual(splitdrive(":foo:bar"), ("", ":foo:bar"))
+
+        self.assertEqual(splitdrive(b"/foo/bar"), (b"", b"/foo/bar"))
+        self.assertEqual(splitdrive(b"foo:bar"), (b"", b"foo:bar"))
+        self.assertEqual(splitdrive(b":foo:bar"), (b"", b":foo:bar"))
+
+    def test_expandvars(self):
+        if self.pathmodule.__name__ == 'macpath':
+            self.skipTest('macpath.expandvars is a stub')
+        expandvars = self.pathmodule.expandvars
+        with support.EnvironmentVarGuard() as env:
+            env.clear()
+            env["foo"] = "bar"
+            env["{foo"] = "baz1"
+            env["{foo}"] = "baz2"
+            self.assertEqual(expandvars("foo"), "foo")
+            self.assertEqual(expandvars("$foo bar"), "bar bar")
+            self.assertEqual(expandvars("${foo}bar"), "barbar")
+            self.assertEqual(expandvars("$[foo]bar"), "$[foo]bar")
+            self.assertEqual(expandvars("$bar bar"), "$bar bar")
+            self.assertEqual(expandvars("$?bar"), "$?bar")
+            self.assertEqual(expandvars("${foo}bar"), "barbar")
+            self.assertEqual(expandvars("$foo}bar"), "bar}bar")
+            self.assertEqual(expandvars("${foo"), "${foo")
+            self.assertEqual(expandvars("${{foo}}"), "baz1}")
+            self.assertEqual(expandvars("$foo$foo"), "barbar")
+            self.assertEqual(expandvars("$bar$bar"), "$bar$bar")
+
+            self.assertEqual(expandvars(b"foo"), b"foo")
+            self.assertEqual(expandvars(b"$foo bar"), b"bar bar")
+            self.assertEqual(expandvars(b"${foo}bar"), b"barbar")
+            self.assertEqual(expandvars(b"$[foo]bar"), b"$[foo]bar")
+            self.assertEqual(expandvars(b"$bar bar"), b"$bar bar")
+            self.assertEqual(expandvars(b"$?bar"), b"$?bar")
+            self.assertEqual(expandvars(b"${foo}bar"), b"barbar")
+            self.assertEqual(expandvars(b"$foo}bar"), b"bar}bar")
+            self.assertEqual(expandvars(b"${foo"), b"${foo")
+            self.assertEqual(expandvars(b"${{foo}}"), b"baz1}")
+            self.assertEqual(expandvars(b"$foo$foo"), b"barbar")
+            self.assertEqual(expandvars(b"$bar$bar"), b"$bar$bar")
+
+    def test_abspath(self):
+        self.assertIn("foo", self.pathmodule.abspath("foo"))
+        self.assertIn(b"foo", self.pathmodule.abspath(b"foo"))
+
+        # Abspath returns bytes when the arg is bytes
+        for path in (b'', b'foo', b'f\xf2\xf2', b'/foo', b'C:\\'):
+            self.assertIsInstance(self.pathmodule.abspath(path), bytes)
+
+    def test_realpath(self):
+        self.assertIn("foo", self.pathmodule.realpath("foo"))
+        self.assertIn(b"foo", self.pathmodule.realpath(b"foo"))
+
+    def test_normpath_issue5827(self):
+        # Make sure normpath preserves unicode
+        for path in ('', '.', '/', '\\', '///foo/.//bar//'):
+            self.assertIsInstance(self.pathmodule.normpath(path), str)
+
+    def test_abspath_issue3426(self):
+        # Check that abspath returns unicode when the arg is unicode
+        # with both ASCII and non-ASCII cwds.
+        abspath = self.pathmodule.abspath
+        for path in ('', 'fuu', 'f\xf9\xf9', '/fuu', 'U:\\'):
+            self.assertIsInstance(abspath(path), str)
+
+        unicwd = '\xe7w\xf0'
+        try:
+            fsencoding = support.TESTFN_ENCODING or "ascii"
+            unicwd.encode(fsencoding)
+        except (AttributeError, UnicodeEncodeError):
+            # FS encoding is probably ASCII
+            pass
+        else:
+            with support.temp_cwd(unicwd):
+                for path in ('', 'fuu', 'f\xf9\xf9', '/fuu', 'U:\\'):
+                    self.assertIsInstance(abspath(path), str)
+
+        # Test non-ASCII, non-UTF8 bytes in the path.
+        with support.temp_cwd('\xe7w\xf0'):
+            self.test_abspath()
 
-            self.assertRaises(TypeError, genericpath.samefile)
 
 def test_main():
-    support.run_unittest(AllCommonTest)
+    support.run_unittest(GenericTest)
+
 
 if __name__=="__main__":
     test_main()
diff --git a/Lib/test/test_macpath.py b/Lib/test/test_macpath.py
index 2c737583274..b36ba005d11 100644
--- a/Lib/test/test_macpath.py
+++ b/Lib/test/test_macpath.py
@@ -1,5 +1,5 @@
 import macpath
-from test import support
+from test import support, test_genericpath
 import unittest
 
 
@@ -139,8 +139,13 @@ class MacPathTestCase(unittest.TestCase):
         self.assertEqual(normpath(b"a:"), b"a:")
         self.assertEqual(normpath(b"a:b:"), b"a:b")
 
+
+class MacCommonTest(test_genericpath.CommonTest):
+    pathmodule = macpath
+
+
 def test_main():
-    support.run_unittest(MacPathTestCase)
+    support.run_unittest(MacPathTestCase, MacCommonTest)
 
 
 if __name__ == "__main__":
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 94a7d9e14ef..c83b45f3e3e 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -1,7 +1,7 @@
 import ntpath
 import os
 from test.support import verbose, TestFailed
-import test.support as support
+from test import support, test_genericpath
 import unittest
 
 
@@ -174,7 +174,6 @@ class TestNtpath(unittest.TestCase):
         tester("ntpath.normpath('C:////a/b')", r'C:\a\b')
         tester("ntpath.normpath('//machine/share//a/b')", r'\\machine\share\a\b')
 
-
     def test_expandvars(self):
         with support.EnvironmentVarGuard() as env:
             env.clear()
@@ -236,8 +235,13 @@ class TestNtpath(unittest.TestCase):
         tester('ntpath.relpath("/a/b", "/a/b")', '.')
 
 
+class NtCommonTest(test_genericpath.CommonTest):
+    pathmodule = ntpath
+    attributes = ['relpath', 'splitunc']
+
+
 def test_main():
-    support.run_unittest(TestNtpath)
+    support.run_unittest(TestNtpath, NtCommonTest)
 
 
 if __name__ == "__main__":
diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
index 1b1167a0061..2d845a822ac 100644
--- a/Lib/test/test_posixpath.py
+++ b/Lib/test/test_posixpath.py
@@ -1,5 +1,5 @@
 import unittest
-from test import support
+from test import support, test_genericpath
 
 import posixpath, os
 from posixpath import realpath, abspath, join, dirname, basename, relpath
@@ -25,16 +25,6 @@ class PosixPathTest(unittest.TestCase):
             support.unlink(support.TESTFN + suffix)
             safe_rmdir(support.TESTFN + suffix)
 
-    def test_normcase(self):
-        # Check that normcase() is idempotent
-        p = "FoO/./BaR"
-        self.assertEqual(p, posixpath.normcase(p))
-
-        p = b"FoO/./BaR"
-        self.assertEqual(p, posixpath.normcase(p))
-
-        self.assertRaises(TypeError, posixpath.normcase)
-
     def test_join(self):
         self.assertEqual(posixpath.join("/foo", "bar", "/bar", "baz"),
                          "/bar/baz")
@@ -49,16 +39,9 @@ class PosixPathTest(unittest.TestCase):
         self.assertEqual(posixpath.join(b"/foo/", b"bar/", b"baz/"),
                          b"/foo/bar/baz/")
 
-        self.assertRaises(TypeError, posixpath.join)
         self.assertRaises(TypeError, posixpath.join, b"bytes", "str")
         self.assertRaises(TypeError, posixpath.join, "str", b"bytes")
 
-    def test_splitdrive(self):
-        self.assertEqual(posixpath.splitdrive("/foo/bar"), ("", "/foo/bar"))
-        self.assertEqual(posixpath.splitdrive(b"/foo/bar"), (b"", b"/foo/bar"))
-
-        self.assertRaises(TypeError, posixpath.splitdrive)
-
     def test_split(self):
         self.assertEqual(posixpath.split("/foo/bar"), ("/foo", "bar"))
         self.assertEqual(posixpath.split("/"), ("/", ""))
@@ -72,8 +55,6 @@ class PosixPathTest(unittest.TestCase):
         self.assertEqual(posixpath.split(b"////foo"), (b"////", b"foo"))
         self.assertEqual(posixpath.split(b"//foo//bar"), (b"//foo", b"bar"))
 
-        self.assertRaises(TypeError, posixpath.split)
-
     def splitextTest(self, path, filename, ext):
         self.assertEqual(posixpath.splitext(path), (filename, ext))
         self.assertEqual(posixpath.splitext("/" + path), ("/" + filename, ext))
@@ -115,7 +96,6 @@ class PosixPathTest(unittest.TestCase):
         self.splitextTest("..", "..", "")
         self.splitextTest("........", "........", "")
         self.splitextTest("", "", "")
-        self.assertRaises(TypeError, posixpath.splitext)
 
     def test_isabs(self):
         self.assertIs(posixpath.isabs(""), False)
@@ -130,8 +110,6 @@ class PosixPathTest(unittest.TestCase):
         self.assertIs(posixpath.isabs(b"/foo/bar"), True)
         self.assertIs(posixpath.isabs(b"foo/bar"), False)
 
-        self.assertRaises(TypeError, posixpath.isabs)
-
     def test_basename(self):
         self.assertEqual(posixpath.basename("/foo/bar"), "bar")
         self.assertEqual(posixpath.basename("/"), "")
@@ -145,8 +123,6 @@ class PosixPathTest(unittest.TestCase):
         self.assertEqual(posixpath.basename(b"////foo"), b"foo")
         self.assertEqual(posixpath.basename(b"//foo//bar"), b"bar")
 
-        self.assertRaises(TypeError, posixpath.basename)
-
     def test_dirname(self):
         self.assertEqual(posixpath.dirname("/foo/bar"), "/foo")
         self.assertEqual(posixpath.dirname("/"), "/")
@@ -160,8 +136,6 @@ class PosixPathTest(unittest.TestCase):
         self.assertEqual(posixpath.dirname(b"////foo"), b"////")
         self.assertEqual(posixpath.dirname(b"//foo//bar"), b"//foo")
 
-        self.assertRaises(TypeError, posixpath.dirname)
-
     def test_commonprefix(self):
         self.assertEqual(
             posixpath.commonprefix([]),
@@ -252,56 +226,6 @@ class PosixPathTest(unittest.TestCase):
             if not f.close():
                 f.close()
 
-        self.assertRaises(TypeError, posixpath.islink)
-
-    def test_exists(self):
-        self.assertIs(posixpath.exists(support.TESTFN), False)
-        f = open(support.TESTFN, "wb")
-        try:
-            f.write(b"foo")
-            f.close()
-            self.assertIs(posixpath.exists(support.TESTFN), True)
-            self.assertIs(posixpath.lexists(support.TESTFN), True)
-        finally:
-            if not f.close():
-                f.close()
-
-        self.assertRaises(TypeError, posixpath.exists)
-
-    def test_isdir(self):
-        self.assertIs(posixpath.isdir(support.TESTFN), False)
-        f = open(support.TESTFN, "wb")
-        try:
-            f.write(b"foo")
-            f.close()
-            self.assertIs(posixpath.isdir(support.TESTFN), False)
-            os.remove(support.TESTFN)
-            os.mkdir(support.TESTFN)
-            self.assertIs(posixpath.isdir(support.TESTFN), True)
-            os.rmdir(support.TESTFN)
-        finally:
-            if not f.close():
-                f.close()
-
-        self.assertRaises(TypeError, posixpath.isdir)
-
-    def test_isfile(self):
-        self.assertIs(posixpath.isfile(support.TESTFN), False)
-        f = open(support.TESTFN, "wb")
-        try:
-            f.write(b"foo")
-            f.close()
-            self.assertIs(posixpath.isfile(support.TESTFN), True)
-            os.remove(support.TESTFN)
-            os.mkdir(support.TESTFN)
-            self.assertIs(posixpath.isfile(support.TESTFN), False)
-            os.rmdir(support.TESTFN)
-        finally:
-            if not f.close():
-                f.close()
-
-        self.assertRaises(TypeError, posixpath.isdir)
-
     def test_samefile(self):
         f = open(support.TESTFN + "1", "wb")
         try:
@@ -343,8 +267,6 @@ class PosixPathTest(unittest.TestCase):
             if not f.close():
                 f.close()
 
-        self.assertRaises(TypeError, posixpath.samefile)
-
     def test_samestat(self):
         f = open(support.TESTFN + "1", "wb")
         try:
@@ -384,13 +306,9 @@ class PosixPathTest(unittest.TestCase):
             if not f.close():
                 f.close()
 
-        self.assertRaises(TypeError, posixpath.samestat)
-
     def test_ismount(self):
         self.assertIs(posixpath.ismount("/"), True)
 
-        self.assertRaises(TypeError, posixpath.ismount)
-
     def test_expanduser(self):
         self.assertEqual(posixpath.expanduser("foo"), "foo")
         self.assertEqual(posixpath.expanduser(b"foo"), b"foo")
@@ -420,41 +338,6 @@ class PosixPathTest(unittest.TestCase):
                 env['HOME'] = '/'
                 self.assertEqual(posixpath.expanduser("~"), "/")
 
-        self.assertRaises(TypeError, posixpath.expanduser)
-
-    def test_expandvars(self):
-        with support.EnvironmentVarGuard() as env:
-            env.clear()
-            env["foo"] = "bar"
-            env["{foo"] = "baz1"
-            env["{foo}"] = "baz2"
-            self.assertEqual(posixpath.expandvars("foo"), "foo")
-            self.assertEqual(posixpath.expandvars("$foo bar"), "bar bar")
-            self.assertEqual(posixpath.expandvars("${foo}bar"), "barbar")
-            self.assertEqual(posixpath.expandvars("$[foo]bar"), "$[foo]bar")
-            self.assertEqual(posixpath.expandvars("$bar bar"), "$bar bar")
-            self.assertEqual(posixpath.expandvars("$?bar"), "$?bar")
-            self.assertEqual(posixpath.expandvars("${foo}bar"), "barbar")
-            self.assertEqual(posixpath.expandvars("$foo}bar"), "bar}bar")
-            self.assertEqual(posixpath.expandvars("${foo"), "${foo")
-            self.assertEqual(posixpath.expandvars("${{foo}}"), "baz1}")
-            self.assertEqual(posixpath.expandvars("$foo$foo"), "barbar")
-            self.assertEqual(posixpath.expandvars("$bar$bar"), "$bar$bar")
-
-            self.assertEqual(posixpath.expandvars(b"foo"), b"foo")
-            self.assertEqual(posixpath.expandvars(b"$foo bar"), b"bar bar")
-            self.assertEqual(posixpath.expandvars(b"${foo}bar"), b"barbar")
-            self.assertEqual(posixpath.expandvars(b"$[foo]bar"), b"$[foo]bar")
-            self.assertEqual(posixpath.expandvars(b"$bar bar"), b"$bar bar")
-            self.assertEqual(posixpath.expandvars(b"$?bar"), b"$?bar")
-            self.assertEqual(posixpath.expandvars(b"${foo}bar"), b"barbar")
-            self.assertEqual(posixpath.expandvars(b"$foo}bar"), b"bar}bar")
-            self.assertEqual(posixpath.expandvars(b"${foo"), b"${foo")
-            self.assertEqual(posixpath.expandvars(b"${{foo}}"), b"baz1}")
-            self.assertEqual(posixpath.expandvars(b"$foo$foo"), b"barbar")
-            self.assertEqual(posixpath.expandvars(b"$bar$bar"), b"$bar$bar")
-            self.assertRaises(TypeError, posixpath.expandvars)
-
     def test_normpath(self):
         self.assertEqual(posixpath.normpath(""), ".")
         self.assertEqual(posixpath.normpath("/"), "/")
@@ -475,19 +358,6 @@ class PosixPathTest(unittest.TestCase):
         self.assertEqual(posixpath.normpath(b"///..//./foo/.//bar"),
                          b"/foo/bar")
 
-        self.assertRaises(TypeError, posixpath.normpath)
-
-    def test_abspath(self):
-        self.assertIn("foo", posixpath.abspath("foo"))
-        self.assertIn(b"foo", posixpath.abspath(b"foo"))
-
-        self.assertRaises(TypeError, posixpath.abspath)
-
-    def test_realpath(self):
-        self.assertIn("foo", realpath("foo"))
-        self.assertIn(b"foo", realpath(b"foo"))
-        self.assertRaises(TypeError, posixpath.realpath)
-
     if hasattr(os, "symlink"):
         def test_realpath_basic(self):
             # Basic operation.
@@ -624,8 +494,15 @@ class PosixPathTest(unittest.TestCase):
         finally:
             os.getcwdb = real_getcwdb
 
+
+class PosixCommonTest(test_genericpath.CommonTest):
+    pathmodule = posixpath
+    attributes = ['relpath', 'samefile', 'sameopenfile', 'samestat']
+
+
 def test_main():
-    support.run_unittest(PosixPathTest)
+    support.run_unittest(PosixPathTest, PosixCommonTest)
+
 
 if __name__=="__main__":
     test_main()
diff --git a/Misc/NEWS b/Misc/NEWS
index de9e4f2250d..70222809344 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -847,6 +847,9 @@ Documentation
 Tests
 -----
 
+- The four path modules (genericpath, macpath, ntpath, posixpath) share a
+  common TestCase for some tests: test_genericpath.CommonTest.
+
 - Print platform information when running the whole test suite, or using
   the --verbose flag.