Implemented PEP 405 (Python virtual environments).
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 2606607..8161b94 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -564,7 +564,7 @@
         random.shuffle(selected)
     if trace:
         import trace, tempfile
-        tracer = trace.Trace(ignoredirs=[sys.prefix, sys.exec_prefix,
+        tracer = trace.Trace(ignoredirs=[sys.base_prefix, sys.base_exec_prefix,
                                          tempfile.gettempdir()],
                              trace=False, count=True)
 
diff --git a/Lib/test/test_cmd.py b/Lib/test/test_cmd.py
index 3a46355..6618535 100644
--- a/Lib/test/test_cmd.py
+++ b/Lib/test/test_cmd.py
@@ -228,7 +228,7 @@
 
 def test_coverage(coverdir):
     trace = support.import_module('trace')
-    tracer=trace.Trace(ignoredirs=[sys.prefix, sys.exec_prefix,],
+    tracer=trace.Trace(ignoredirs=[sys.base_prefix, sys.base_exec_prefix,],
                         trace=0, count=1)
     tracer.run('reload(cmd);test_main()')
     r=tracer.results()
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index cdcd389..44b9554 100644
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -2543,7 +2543,7 @@
 
 def test_coverage(coverdir):
     trace = support.import_module('trace')
-    tracer = trace.Trace(ignoredirs=[sys.prefix, sys.exec_prefix,],
+    tracer = trace.Trace(ignoredirs=[sys.base_prefix, sys.base_exec_prefix,],
                          trace=0, count=1)
     tracer.run('test_main()')
     r = tracer.results()
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 0f8d1ca..c21d15b 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -189,6 +189,8 @@
         p.wait()
         self.assertEqual(p.stderr, None)
 
+    @unittest.skipIf(sys.base_prefix != sys.prefix,
+                     'Test is not venv-compatible')
     def test_executable_with_cwd(self):
         python_dir = os.path.dirname(os.path.realpath(sys.executable))
         p = subprocess.Popen(["somethingyoudonthave", "-c",
@@ -197,6 +199,8 @@
         p.wait()
         self.assertEqual(p.returncode, 47)
 
+    @unittest.skipIf(sys.base_prefix != sys.prefix,
+                     'Test is not venv-compatible')
     @unittest.skipIf(sysconfig.is_python_build(),
                      "need an installed Python. See #7774")
     def test_executable_without_cwd(self):
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 71dbd29..e3629ff 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -419,6 +419,7 @@
         self.assertIsInstance(sys.builtin_module_names, tuple)
         self.assertIsInstance(sys.copyright, str)
         self.assertIsInstance(sys.exec_prefix, str)
+        self.assertIsInstance(sys.base_exec_prefix, str)
         self.assertIsInstance(sys.executable, str)
         self.assertEqual(len(sys.float_info), 11)
         self.assertEqual(sys.float_info.radix, 2)
@@ -450,6 +451,7 @@
         self.assertEqual(sys.maxunicode, 0x10FFFF)
         self.assertIsInstance(sys.platform, str)
         self.assertIsInstance(sys.prefix, str)
+        self.assertIsInstance(sys.base_prefix, str)
         self.assertIsInstance(sys.version, str)
         vi = sys.version_info
         self.assertIsInstance(vi[:], tuple)
@@ -541,6 +543,8 @@
         out = p.communicate()[0].strip()
         self.assertEqual(out, b'?')
 
+    @unittest.skipIf(sys.base_prefix != sys.prefix,
+                     'Test is not venv-compatible')
     def test_executable(self):
         # sys.executable should be absolute
         self.assertEqual(os.path.abspath(sys.executable), sys.executable)
diff --git a/Lib/test/test_sysconfig.py b/Lib/test/test_sysconfig.py
index a2e6fbc..e583793 100644
--- a/Lib/test/test_sysconfig.py
+++ b/Lib/test/test_sysconfig.py
@@ -260,12 +260,17 @@
         # the global scheme mirrors the distinction between prefix and
         # exec-prefix but not the user scheme, so we have to adapt the paths
         # before comparing (issue #9100)
-        adapt = sys.prefix != sys.exec_prefix
+        adapt = sys.base_prefix != sys.base_exec_prefix
         for name in ('stdlib', 'platstdlib', 'purelib', 'platlib'):
             global_path = get_path(name, 'posix_prefix')
             if adapt:
-                global_path = global_path.replace(sys.exec_prefix, sys.prefix)
-                base = base.replace(sys.exec_prefix, sys.prefix)
+                global_path = global_path.replace(sys.exec_prefix, sys.base_prefix)
+                base = base.replace(sys.exec_prefix, sys.base_prefix)
+            elif sys.base_prefix != sys.prefix:
+                # virtual environment? Likewise, we have to adapt the paths
+                # before comparing
+                global_path = global_path.replace(sys.base_prefix, sys.prefix)
+                base = base.replace(sys.base_prefix, sys.prefix)
             user_path = get_path(name, 'posix_user')
             self.assertEqual(user_path, global_path.replace(base, user, 1))
 
diff --git a/Lib/test/test_trace.py b/Lib/test/test_trace.py
index fa0d48c..ac3a1a3 100644
--- a/Lib/test/test_trace.py
+++ b/Lib/test/test_trace.py
@@ -316,8 +316,8 @@
         # Ignore all files, nothing should be traced nor printed
         libpath = os.path.normpath(os.path.dirname(os.__file__))
         # sys.prefix does not work when running from a checkout
-        tracer = trace.Trace(ignoredirs=[sys.prefix, sys.exec_prefix, libpath],
-                             trace=0, count=1)
+        tracer = trace.Trace(ignoredirs=[sys.base_prefix, sys.base_exec_prefix,
+                             libpath], trace=0, count=1)
         with captured_stdout() as stdout:
             self._coverage(tracer)
         if os.path.exists(TESTFN):
diff --git a/Lib/test/test_venv.py b/Lib/test/test_venv.py
new file mode 100644
index 0000000..fae62ed
--- /dev/null
+++ b/Lib/test/test_venv.py
@@ -0,0 +1,139 @@
+#!/usr/bin/env python
+#
+# Copyright 2011 by Vinay Sajip. All Rights Reserved.
+#
+# Permission to use, copy, modify, and distribute this software and its
+# documentation for any purpose and without fee is hereby granted,
+# provided that the above copyright notice appear in all copies and that
+# both that copyright notice and this permission notice appear in
+# supporting documentation, and that the name of Vinay Sajip
+# not be used in advertising or publicity pertaining to distribution
+# of the software without specific, written prior permission.
+# VINAY SAJIP DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
+# ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
+# VINAY SAJIP BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
+# ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
+# IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+"""Test harness for the venv module. Run all tests.
+
+Copyright (C) 2011 Vinay Sajip. All Rights Reserved.
+"""
+
+import os
+import os.path
+import shutil
+import sys
+import tempfile
+from test.support import (captured_stdout, captured_stderr, run_unittest,
+                          can_symlink)
+import unittest
+import venv
+
+class BaseTest(unittest.TestCase):
+    """Base class for venv tests."""
+
+    def setUp(self):
+        self.env_dir = tempfile.mkdtemp()
+        if os.name == 'nt':
+            self.bindir = 'Scripts'
+            self.ps3name = 'pysetup3-script.py'
+            self.lib = ('Lib',)
+            self.include = 'Include'
+            self.exe = 'python.exe'
+        else:
+            self.bindir = 'bin'
+            self.ps3name = 'pysetup3'
+            self.lib = ('lib', 'python%s' % sys.version[:3])
+            self.include = 'include'
+            self.exe = 'python'
+
+    def tearDown(self):
+        shutil.rmtree(self.env_dir)
+
+    def run_with_capture(self, func, *args, **kwargs):
+        with captured_stdout() as output:
+            with captured_stderr() as error:
+                func(*args, **kwargs)
+        return output.getvalue(), error.getvalue()
+
+    def get_env_file(self, *args):
+        return os.path.join(self.env_dir, *args)
+
+    def get_text_file_contents(self, *args):
+        with open(self.get_env_file(*args), 'r') as f:
+            result = f.read()
+        return result
+
+class BasicTest(BaseTest):
+    """Test venv module functionality."""
+
+    def test_defaults(self):
+        """
+        Test the create function with default arguments.
+        """
+        def isdir(*args):
+            fn = self.get_env_file(*args)
+            self.assertTrue(os.path.isdir(fn))
+
+        shutil.rmtree(self.env_dir)
+        self.run_with_capture(venv.create, self.env_dir)
+        isdir(self.bindir)
+        isdir(self.include)
+        isdir(*self.lib)
+        data = self.get_text_file_contents('pyvenv.cfg')
+        if sys.platform == 'darwin' and ('__PYTHONV_LAUNCHER__'
+                                         in os.environ):
+            executable =  os.environ['__PYTHONV_LAUNCHER__']
+        else:
+            executable = sys.executable
+        path = os.path.dirname(executable)
+        self.assertIn('home = %s' % path, data)
+        data = self.get_text_file_contents(self.bindir, self.ps3name)
+        self.assertTrue(data.startswith('#!%s%s' % (self.env_dir, os.sep)))
+        fn = self.get_env_file(self.bindir, self.exe)
+        self.assertTrue(os.path.exists(fn))
+
+    def test_overwrite_existing(self):
+        """
+        Test control of overwriting an existing environment directory.
+        """
+        self.assertRaises(ValueError, venv.create, self.env_dir)
+        builder = venv.EnvBuilder(clear=True)
+        builder.create(self.env_dir)
+
+    def test_isolation(self):
+        """
+        Test isolation from system site-packages
+        """
+        for ssp, s in ((True, 'true'), (False, 'false')):
+            builder = venv.EnvBuilder(clear=True, system_site_packages=ssp)
+            builder.create(self.env_dir)
+            data = self.get_text_file_contents('pyvenv.cfg')
+            self.assertIn('include-system-site-packages = %s\n' % s, data)
+
+    @unittest.skipUnless(can_symlink(), 'Needs symlinks')
+    def test_symlinking(self):
+        """
+        Test symlinking works as expected
+        """
+        for usl in (False, True):
+            builder = venv.EnvBuilder(clear=True, symlinks=usl)
+            if (usl and sys.platform == 'darwin' and
+                '__PYTHONV_LAUNCHER__' in os.environ):
+                self.assertRaises(ValueError, builder.create, self.env_dir)
+            else:
+                builder.create(self.env_dir)
+                fn = self.get_env_file(self.bindir, self.exe)
+                # Don't test when False, because e.g. 'python' is always
+                # symlinked to 'python3.3' in the env, even when symlinking in
+                # general isn't wanted.
+                if usl:
+                    self.assertTrue(os.path.islink(fn))
+
+def test_main():
+    run_unittest(BasicTest)
+
+if __name__ == "__main__":
+    test_main()