diff -r adb6b029b102 Lib/test/__init__.py
--- a/Lib/test/__init__.py	Wed Mar 09 15:02:31 2016 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,1 +0,0 @@
-# Dummy file to make this directory a package.
diff -r adb6b029b102 Lib/test/libregrtest/setup.py
--- a/Lib/test/libregrtest/setup.py	Wed Mar 09 15:02:31 2016 +0100
+++ b/Lib/test/libregrtest/setup.py	Fri Mar 11 12:53:50 2016 +0100
@@ -29,6 +29,9 @@ def setup_tests(ns):
     replace_stdout()
     support.record_original_stdout(sys.stdout)
 
+    if ns.testdir:
+        sys.path.insert(0, os.path.dirname(ns.testdir))
+
     # Some times __path__ and __file__ are not absolute (e.g. while running from
     # Lib/) and, if we change the CWD to run the tests in a temporary dir, some
     # imports might fail.  This affects only the modules imported before os.chdir().
diff -r adb6b029b102 Lib/test/test_regrtest.py
--- a/Lib/test/test_regrtest.py	Wed Mar 09 15:02:31 2016 +0100
+++ b/Lib/test/test_regrtest.py	Fri Mar 11 12:53:50 2016 +0100
@@ -15,6 +15,7 @@ import re
 import subprocess
 import sys
 import sysconfig
+import tempfile
 import textwrap
 import unittest
 from test import libregrtest
@@ -306,9 +307,18 @@ class BaseTestCase(unittest.TestCase):
     TESTNAME_PREFIX = 'test_regrtest_'
     TESTNAME_REGEX = r'test_[a-z0-9_]+'
 
+    def create_testdir(self):
+        self.tmpdir = tempfile.mkdtemp()
+        self.addCleanup(support.rmtree, self.tmpdir)
+
+        self.tmptestdir = os.path.join(self.tmpdir, 'test')
+        os.mkdir(self.tmptestdir)
+
     def setUp(self):
         self.testdir = os.path.realpath(os.path.dirname(__file__))
 
+        self.create_testdir()
+
         # When test_regrtest is interrupted by CTRL+c, it can leave
         # temporary test files
         remove = [entry.path
@@ -327,7 +337,7 @@ class BaseTestCase(unittest.TestCase):
         # test_regrtest cannot be run twice in parallel because
         # of setUp() and create_test()
         name = self.TESTNAME_PREFIX + "%s_%s" % (os.getpid(), name)
-        path = os.path.join(self.testdir, name + '.py')
+        path = os.path.join(self.tmptestdir, name + '.py')
 
         self.addCleanup(support.unlink, path)
         # Use 'x' mode to ensure that we do not override existing tests
@@ -441,7 +451,9 @@ class BaseTestCase(unittest.TestCase):
 
 
     def run_python(self, args, **kw):
-        args = [sys.executable, '-X', 'faulthandler', '-I', *args]
+        args = [sys.executable, '-X', 'faulthandler',
+                #'-I',
+                *args]
         proc = self.run_command(args, **kw)
         return proc.stdout
 
@@ -461,7 +473,7 @@ class ProgramsTestCase(BaseTestCase):
         self.tests = [self.create_test() for index in range(self.NTEST)]
 
         self.python_args = ['-Wd', '-E', '-bb']
-        self.regrtest_args = ['-uall', '-rwW']
+        self.regrtest_args = ['-uall', '-rwW', '--testdir=%s' % self.tmptestdir]
         if hasattr(faulthandler, 'dump_traceback_later'):
             self.regrtest_args.extend(('--timeout', '3600', '-j4'))
         if sys.platform == 'win32':
@@ -518,7 +530,8 @@ class ProgramsTestCase(BaseTestCase):
     def test_tools_script_run_tests(self):
         # Tools/scripts/run_tests.py
         script = os.path.join(ROOT_DIR, 'Tools', 'scripts', 'run_tests.py')
-        self.run_tests([script, *self.tests])
+        args = [script, '--testdir=%s' % self.tmptestdir, *self.tests]
+        self.run_tests(args)
 
     def run_batch(self, *args):
         proc = self.run_command(args)
@@ -554,8 +567,9 @@ class ArgsTestCase(BaseTestCase):
     Test arguments of the Python test suite.
     """
 
-    def run_tests(self, *args, **kw):
-        return self.run_python(['-m', 'test', *args], **kw)
+    def run_tests(self, *testargs, **kw):
+        cmdargs = ['-m', 'test', '--testdir=%s' % self.tmptestdir, *testargs]
+        return self.run_python(cmdargs, **kw)
 
     def test_failing_test(self):
         # test a failing test