Issue #25220: Move most regrtest.py code to libregrtest

8 files changed, 1318 insertions, 1272 deletions

diff --git a/Lib/test/libregrtest/__init__.py b/Lib/test/libregrtest/__init__.py
index 554aeede4a..a882ed2960 100644
--- a/Lib/test/libregrtest/__init__.py
+++ b/Lib/test/libregrtest/__init__.py
@@ -1 +1,2 @@
 from test.libregrtest.cmdline import _parse_args, RESOURCE_NAMES
+from test.libregrtest.main import main_in_temp_cwd
diff --git a/Lib/test/libregrtest/cmdline.py b/Lib/test/libregrtest/cmdline.py
index 94649965a5..19c52a2fe6 100644
--- a/Lib/test/libregrtest/cmdline.py
+++ b/Lib/test/libregrtest/cmdline.py
@@ -1,9 +1,9 @@
 import argparse
 import faulthandler
 import os
-
 from test import support
 
+
 USAGE = """\
 python -m test [options] [test_name1 [test_name2 ...]]
 python path/to/Lib/test/regrtest.py [options] [test_name1 [test_name2 ...]]
diff --git a/Lib/test/libregrtest/main.py b/Lib/test/libregrtest/main.py
new file mode 100644
index 0000000000..5d34cffd49
--- /dev/null
+++ b/Lib/test/libregrtest/main.py
@@ -0,0 +1,547 @@
+import faulthandler
+import json
+import os
+import re
+import sys
+import tempfile
+import sysconfig
+import signal
+import random
+import platform
+import traceback
+import unittest
+from test.libregrtest.runtest import (
+    findtests, runtest, run_test_in_subprocess,
+    STDTESTS, NOTTESTS,
+    PASSED, FAILED, ENV_CHANGED, SKIPPED,
+    RESOURCE_DENIED, INTERRUPTED, CHILD_ERROR)
+from test.libregrtest.refleak import warm_caches
+from test.libregrtest.cmdline import _parse_args
+from test import support
+try:
+    import threading
+except ImportError:
+    threading = None
+
+
+# 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().
+# These modules are searched first in sys.path[0] (so '' -- the CWD) and if
+# they are found in the CWD their __file__ and __path__ will be relative (this
+# happens before the chdir).  All the modules imported after the chdir, are
+# not found in the CWD, and since the other paths in sys.path[1:] are absolute
+# (site.py absolutize them), the __file__ and __path__ will be absolute too.
+# Therefore it is necessary to absolutize manually the __file__ and __path__ of
+# the packages to prevent later imports to fail when the CWD is different.
+for module in sys.modules.values():
+    if hasattr(module, '__path__'):
+        module.__path__ = [os.path.abspath(path) for path in module.__path__]
+    if hasattr(module, '__file__'):
+        module.__file__ = os.path.abspath(module.__file__)
+
+
+# MacOSX (a.k.a. Darwin) has a default stack size that is too small
+# for deeply recursive regular expressions.  We see this as crashes in
+# the Python test suite when running test_re.py and test_sre.py.  The
+# fix is to set the stack limit to 2048.
+# This approach may also be useful for other Unixy platforms that
+# suffer from small default stack limits.
+if sys.platform == 'darwin':
+    try:
+        import resource
+    except ImportError:
+        pass
+    else:
+        soft, hard = resource.getrlimit(resource.RLIMIT_STACK)
+        newsoft = min(hard, max(soft, 1024*2048))
+        resource.setrlimit(resource.RLIMIT_STACK, (newsoft, hard))
+
+
+# When tests are run from the Python build directory, it is best practice
+# to keep the test files in a subfolder.  This eases the cleanup of leftover
+# files using the "make distclean" command.
+if sysconfig.is_python_build():
+    TEMPDIR = os.path.join(sysconfig.get_config_var('srcdir'), 'build')
+else:
+    TEMPDIR = tempfile.gettempdir()
+TEMPDIR = os.path.abspath(TEMPDIR)
+
+
+def main(tests=None, **kwargs):
+    """Execute a test suite.
+
+    This also parses command-line options and modifies its behavior
+    accordingly.
+
+    tests -- a list of strings containing test names (optional)
+    testdir -- the directory in which to look for tests (optional)
+
+    Users other than the Python test suite will certainly want to
+    specify testdir; if it's omitted, the directory containing the
+    Python test suite is searched for.
+
+    If the tests argument is omitted, the tests listed on the
+    command-line will be used.  If that's empty, too, then all *.py
+    files beginning with test_ will be used.
+
+    The other default arguments (verbose, quiet, exclude,
+    single, randomize, findleaks, use_resources, trace, coverdir,
+    print_slow, and random_seed) allow programmers calling main()
+    directly to set the values that would normally be set by flags
+    on the command line.
+    """
+    # Display the Python traceback on fatal errors (e.g. segfault)
+    faulthandler.enable(all_threads=True)
+
+    # Display the Python traceback on SIGALRM or SIGUSR1 signal
+    signals = []
+    if hasattr(signal, 'SIGALRM'):
+        signals.append(signal.SIGALRM)
+    if hasattr(signal, 'SIGUSR1'):
+        signals.append(signal.SIGUSR1)
+    for signum in signals:
+        faulthandler.register(signum, chain=True)
+
+    replace_stdout()
+
+    support.record_original_stdout(sys.stdout)
+
+    ns = _parse_args(sys.argv[1:], **kwargs)
+
+    if ns.huntrleaks:
+        # Avoid false positives due to various caches
+        # filling slowly with random data:
+        warm_caches()
+    if ns.memlimit is not None:
+        support.set_memlimit(ns.memlimit)
+    if ns.threshold is not None:
+        import gc
+        gc.set_threshold(ns.threshold)
+    if ns.nowindows:
+        import msvcrt
+        msvcrt.SetErrorMode(msvcrt.SEM_FAILCRITICALERRORS|
+                            msvcrt.SEM_NOALIGNMENTFAULTEXCEPT|
+                            msvcrt.SEM_NOGPFAULTERRORBOX|
+                            msvcrt.SEM_NOOPENFILEERRORBOX)
+        try:
+            msvcrt.CrtSetReportMode
+        except AttributeError:
+            # release build
+            pass
+        else:
+            for m in [msvcrt.CRT_WARN, msvcrt.CRT_ERROR, msvcrt.CRT_ASSERT]:
+                msvcrt.CrtSetReportMode(m, msvcrt.CRTDBG_MODE_FILE)
+                msvcrt.CrtSetReportFile(m, msvcrt.CRTDBG_FILE_STDERR)
+    if ns.wait:
+        input("Press any key to continue...")
+
+    if ns.slaveargs is not None:
+        args, kwargs = json.loads(ns.slaveargs)
+        if kwargs.get('huntrleaks'):
+            unittest.BaseTestSuite._cleanup = False
+        try:
+            result = runtest(*args, **kwargs)
+        except KeyboardInterrupt:
+            result = INTERRUPTED, ''
+        except BaseException as e:
+            traceback.print_exc()
+            result = CHILD_ERROR, str(e)
+        sys.stdout.flush()
+        print()   # Force a newline (just in case)
+        print(json.dumps(result))
+        sys.exit(0)
+
+    good = []
+    bad = []
+    skipped = []
+    resource_denieds = []
+    environment_changed = []
+    interrupted = False
+
+    if ns.findleaks:
+        try:
+            import gc
+        except ImportError:
+            print('No GC available, disabling findleaks.')
+            ns.findleaks = False
+        else:
+            # Uncomment the line below to report garbage that is not
+            # freeable by reference counting alone.  By default only
+            # garbage that is not collectable by the GC is reported.
+            #gc.set_debug(gc.DEBUG_SAVEALL)
+            found_garbage = []
+
+    if ns.huntrleaks:
+        unittest.BaseTestSuite._cleanup = False
+
+    if ns.single:
+        filename = os.path.join(TEMPDIR, 'pynexttest')
+        try:
+            with open(filename, 'r') as fp:
+                next_test = fp.read().strip()
+                tests = [next_test]
+        except OSError:
+            pass
+
+    if ns.fromfile:
+        tests = []
+        with open(os.path.join(support.SAVEDCWD, ns.fromfile)) as fp:
+            count_pat = re.compile(r'\[\s*\d+/\s*\d+\]')
+            for line in fp:
+                line = count_pat.sub('', line)
+                guts = line.split() # assuming no test has whitespace in its name
+                if guts and not guts[0].startswith('#'):
+                    tests.extend(guts)
+
+    # Strip .py extensions.
+    removepy(ns.args)
+    removepy(tests)
+
+    stdtests = STDTESTS[:]
+    nottests = NOTTESTS.copy()
+    if ns.exclude:
+        for arg in ns.args:
+            if arg in stdtests:
+                stdtests.remove(arg)
+            nottests.add(arg)
+        ns.args = []
+
+    # For a partial run, we do not need to clutter the output.
+    if ns.verbose or ns.header or not (ns.quiet or ns.single or tests or ns.args):
+        # Print basic platform information
+        print("==", platform.python_implementation(), *sys.version.split())
+        print("==  ", platform.platform(aliased=True),
+                      "%s-endian" % sys.byteorder)
+        print("==  ", "hash algorithm:", sys.hash_info.algorithm,
+              "64bit" if sys.maxsize > 2**32 else "32bit")
+        print("==  ", os.getcwd())
+        print("Testing with flags:", sys.flags)
+
+    # if testdir is set, then we are not running the python tests suite, so
+    # don't add default tests to be executed or skipped (pass empty values)
+    if ns.testdir:
+        alltests = findtests(ns.testdir, list(), set())
+    else:
+        alltests = findtests(ns.testdir, stdtests, nottests)
+
+    selected = tests or ns.args or alltests
+    if ns.single:
+        selected = selected[:1]
+        try:
+            next_single_test = alltests[alltests.index(selected[0])+1]
+        except IndexError:
+            next_single_test = None
+    # Remove all the selected tests that precede start if it's set.
+    if ns.start:
+        try:
+            del selected[:selected.index(ns.start)]
+        except ValueError:
+            print("Couldn't find starting test (%s), using all tests" % ns.start)
+    if ns.randomize:
+        if ns.random_seed is None:
+            ns.random_seed = random.randrange(10000000)
+        random.seed(ns.random_seed)
+        print("Using random seed", ns.random_seed)
+        random.shuffle(selected)
+    if ns.trace:
+        import trace, tempfile
+        tracer = trace.Trace(ignoredirs=[sys.base_prefix, sys.base_exec_prefix,
+                                         tempfile.gettempdir()],
+                             trace=False, count=True)
+
+    test_times = []
+    support.verbose = ns.verbose      # Tell tests to be moderately quiet
+    support.use_resources = ns.use_resources
+    save_modules = sys.modules.keys()
+
+    def accumulate_result(test, result):
+        ok, test_time = result
+        test_times.append((test_time, test))
+        if ok == PASSED:
+            good.append(test)
+        elif ok == FAILED:
+            bad.append(test)
+        elif ok == ENV_CHANGED:
+            environment_changed.append(test)
+        elif ok == SKIPPED:
+            skipped.append(test)
+        elif ok == RESOURCE_DENIED:
+            skipped.append(test)
+            resource_denieds.append(test)
+
+    if ns.forever:
+        def test_forever(tests=list(selected)):
+            while True:
+                for test in tests:
+                    yield test
+                    if bad:
+                        return
+        tests = test_forever()
+        test_count = ''
+        test_count_width = 3
+    else:
+        tests = iter(selected)
+        test_count = '/{}'.format(len(selected))
+        test_count_width = len(test_count) - 1
+
+    if ns.use_mp:
+        try:
+            from threading import Thread
+        except ImportError:
+            print("Multiprocess option requires thread support")
+            sys.exit(2)
+        from queue import Queue
+        debug_output_pat = re.compile(r"\[\d+ refs, \d+ blocks\]$")
+        output = Queue()
+        pending = MultiprocessTests(tests)
+        def work():
+            # A worker thread.
+            try:
+                while True:
+                    try:
+                        test = next(pending)
+                    except StopIteration:
+                        output.put((None, None, None, None))
+                        return
+                    retcode, stdout, stderr = run_test_in_subprocess(test, ns)
+                    # Strip last refcount output line if it exists, since it
+                    # comes from the shutdown of the interpreter in the subcommand.
+                    stderr = debug_output_pat.sub("", stderr)
+                    stdout, _, result = stdout.strip().rpartition("\n")
+                    if retcode != 0:
+                        result = (CHILD_ERROR, "Exit code %s" % retcode)
+                        output.put((test, stdout.rstrip(), stderr.rstrip(), result))
+                        return
+                    if not result:
+                        output.put((None, None, None, None))
+                        return
+                    result = json.loads(result)
+                    output.put((test, stdout.rstrip(), stderr.rstrip(), result))
+            except BaseException:
+                output.put((None, None, None, None))
+                raise
+        workers = [Thread(target=work) for i in range(ns.use_mp)]
+        for worker in workers:
+            worker.start()
+        finished = 0
+        test_index = 1
+        try:
+            while finished < ns.use_mp:
+                test, stdout, stderr, result = output.get()
+                if test is None:
+                    finished += 1
+                    continue
+                accumulate_result(test, result)
+                if not ns.quiet:
+                    fmt = "[{1:{0}}{2}/{3}] {4}" if bad else "[{1:{0}}{2}] {4}"
+                    print(fmt.format(
+                        test_count_width, test_index, test_count,
+                        len(bad), test))
+                if stdout:
+                    print(stdout)
+                if stderr:
+                    print(stderr, file=sys.stderr)
+                sys.stdout.flush()
+                sys.stderr.flush()
+                if result[0] == INTERRUPTED:
+                    raise KeyboardInterrupt
+                if result[0] == CHILD_ERROR:
+                    raise Exception("Child error on {}: {}".format(test, result[1]))
+                test_index += 1
+        except KeyboardInterrupt:
+            interrupted = True
+            pending.interrupted = True
+        for worker in workers:
+            worker.join()
+    else:
+        for test_index, test in enumerate(tests, 1):
+            if not ns.quiet:
+                fmt = "[{1:{0}}{2}/{3}] {4}" if bad else "[{1:{0}}{2}] {4}"
+                print(fmt.format(
+                    test_count_width, test_index, test_count, len(bad), test))
+                sys.stdout.flush()
+            if ns.trace:
+                # If we're tracing code coverage, then we don't exit with status
+                # if on a false return value from main.
+                tracer.runctx('runtest(test, ns.verbose, ns.quiet, timeout=ns.timeout)',
+                              globals=globals(), locals=vars())
+            else:
+                try:
+                    result = runtest(test, ns.verbose, ns.quiet,
+                                     ns.huntrleaks,
+                                     output_on_failure=ns.verbose3,
+                                     timeout=ns.timeout, failfast=ns.failfast,
+                                     match_tests=ns.match_tests)
+                    accumulate_result(test, result)
+                except KeyboardInterrupt:
+                    interrupted = True
+                    break
+            if ns.findleaks:
+                gc.collect()
+                if gc.garbage:
+                    print("Warning: test created", len(gc.garbage), end=' ')
+                    print("uncollectable object(s).")
+                    # move the uncollectable objects somewhere so we don't see
+                    # them again
+                    found_garbage.extend(gc.garbage)
+                    del gc.garbage[:]
+            # Unload the newly imported modules (best effort finalization)
+            for module in sys.modules.keys():
+                if module not in save_modules and module.startswith("test."):
+                    support.unload(module)
+
+    if interrupted:
+        # print a newline after ^C
+        print()
+        print("Test suite interrupted by signal SIGINT.")
+        omitted = set(selected) - set(good) - set(bad) - set(skipped)
+        print(count(len(omitted), "test"), "omitted:")
+        printlist(omitted)
+    if good and not ns.quiet:
+        if not bad and not skipped and not interrupted and len(good) > 1:
+            print("All", end=' ')
+        print(count(len(good), "test"), "OK.")
+    if ns.print_slow:
+        test_times.sort(reverse=True)
+        print("10 slowest tests:")
+        for time, test in test_times[:10]:
+            print("%s: %.1fs" % (test, time))
+    if bad:
+        print(count(len(bad), "test"), "failed:")
+        printlist(bad)
+    if environment_changed:
+        print("{} altered the execution environment:".format(
+                 count(len(environment_changed), "test")))
+        printlist(environment_changed)
+    if skipped and not ns.quiet:
+        print(count(len(skipped), "test"), "skipped:")
+        printlist(skipped)
+
+    if ns.verbose2 and bad:
+        print("Re-running failed tests in verbose mode")
+        for test in bad[:]:
+            print("Re-running test %r in verbose mode" % test)
+            sys.stdout.flush()
+            try:
+                ns.verbose = True
+                ok = runtest(test, True, ns.quiet, ns.huntrleaks,
+                             timeout=ns.timeout)
+            except KeyboardInterrupt:
+                # print a newline separate from the ^C
+                print()
+                break
+            else:
+                if ok[0] in {PASSED, ENV_CHANGED, SKIPPED, RESOURCE_DENIED}:
+                    bad.remove(test)
+        else:
+            if bad:
+                print(count(len(bad), 'test'), "failed again:")
+                printlist(bad)
+
+    if ns.single:
+        if next_single_test:
+            with open(filename, 'w') as fp:
+                fp.write(next_single_test + '\n')
+        else:
+            os.unlink(filename)
+
+    if ns.trace:
+        r = tracer.results()
+        r.write_results(show_missing=True, summary=True, coverdir=ns.coverdir)
+
+    if ns.runleaks:
+        os.system("leaks %d" % os.getpid())
+
+    sys.exit(len(bad) > 0 or interrupted)
+
+
+# We do not use a generator so multiple threads can call next().
+class MultiprocessTests(object):
+
+    """A thread-safe iterator over tests for multiprocess mode."""
+
+    def __init__(self, tests):
+        self.interrupted = False
+        self.lock = threading.Lock()
+        self.tests = tests
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        with self.lock:
+            if self.interrupted:
+                raise StopIteration('tests interrupted')
+            return next(self.tests)
+
+
+def replace_stdout():
+    """Set stdout encoder error handler to backslashreplace (as stderr error
+    handler) to avoid UnicodeEncodeError when printing a traceback"""
+    import atexit
+
+    stdout = sys.stdout
+    sys.stdout = open(stdout.fileno(), 'w',
+        encoding=stdout.encoding,
+        errors="backslashreplace",
+        closefd=False,
+        newline='\n')
+
+    def restore_stdout():
+        sys.stdout.close()
+        sys.stdout = stdout
+    atexit.register(restore_stdout)
+
+
+def removepy(names):
+    if not names:
+        return
+    for idx, name in enumerate(names):
+        basename, ext = os.path.splitext(name)
+        if ext == '.py':
+            names[idx] = basename
+
+
+def count(n, word):
+    if n == 1:
+        return "%d %s" % (n, word)
+    else:
+        return "%d %ss" % (n, word)
+
+
+def printlist(x, width=70, indent=4):
+    """Print the elements of iterable x to stdout.
+
+    Optional arg width (default 70) is the maximum line length.
+    Optional arg indent (default 4) is the number of blanks with which to
+    begin each line.
+    """
+
+    from textwrap import fill
+    blanks = ' ' * indent
+    # Print the sorted list: 'x' may be a '--random' list or a set()
+    print(fill(' '.join(str(elt) for elt in sorted(x)), width,
+               initial_indent=blanks, subsequent_indent=blanks))
+
+
+def main_in_temp_cwd():
+    """Run main() in a temporary working directory."""
+    if sysconfig.is_python_build():
+        try:
+            os.mkdir(TEMPDIR)
+        except FileExistsError:
+            pass
+
+    # Define a writable temp dir that will be used as cwd while running
+    # the tests. The name of the dir includes the pid to allow parallel
+    # testing (see the -j option).
+    test_cwd = 'test_python_{}'.format(os.getpid())
+    test_cwd = os.path.join(TEMPDIR, test_cwd)
+
+    # Run the tests in a context manager that temporarily changes the CWD to a
+    # temporary and writable directory.  If it's not possible to create or
+    # change the CWD, the original CWD will be used.  The original CWD is
+    # available from support.SAVEDCWD.
+    with support.temp_cwd(test_cwd, quiet=True):
+        main()
diff --git a/Lib/test/libregrtest/refleak.py b/Lib/test/libregrtest/refleak.py
new file mode 100644
index 0000000000..dd0d05d3ec
--- /dev/null
+++ b/Lib/test/libregrtest/refleak.py
@@ -0,0 +1,165 @@
+import os
+import re
+import sys
+import warnings
+from inspect import isabstract
+from test import support
+
+
+def dash_R(the_module, test, indirect_test, huntrleaks):
+    """Run a test multiple times, looking for reference leaks.
+
+    Returns:
+        False if the test didn't leak references; True if we detected refleaks.
+    """
+    # This code is hackish and inelegant, but it seems to do the job.
+    import copyreg
+    import collections.abc
+
+    if not hasattr(sys, 'gettotalrefcount'):
+        raise Exception("Tracking reference leaks requires a debug build "
+                        "of Python")
+
+    # Save current values for dash_R_cleanup() to restore.
+    fs = warnings.filters[:]
+    ps = copyreg.dispatch_table.copy()
+    pic = sys.path_importer_cache.copy()
+    try:
+        import zipimport
+    except ImportError:
+        zdc = None # Run unmodified on platforms without zipimport support
+    else:
+        zdc = zipimport._zip_directory_cache.copy()
+    abcs = {}
+    for abc in [getattr(collections.abc, a) for a in collections.abc.__all__]:
+        if not isabstract(abc):
+            continue
+        for obj in abc.__subclasses__() + [abc]:
+            abcs[obj] = obj._abc_registry.copy()
+
+    nwarmup, ntracked, fname = huntrleaks
+    fname = os.path.join(support.SAVEDCWD, fname)
+    repcount = nwarmup + ntracked
+    rc_deltas = [0] * repcount
+    alloc_deltas = [0] * repcount
+
+    print("beginning", repcount, "repetitions", file=sys.stderr)
+    print(("1234567890"*(repcount//10 + 1))[:repcount], file=sys.stderr)
+    sys.stderr.flush()
+    for i in range(repcount):
+        indirect_test()
+        alloc_after, rc_after = dash_R_cleanup(fs, ps, pic, zdc, abcs)
+        sys.stderr.write('.')
+        sys.stderr.flush()
+        if i >= nwarmup:
+            rc_deltas[i] = rc_after - rc_before
+            alloc_deltas[i] = alloc_after - alloc_before
+        alloc_before, rc_before = alloc_after, rc_after
+    print(file=sys.stderr)
+    # These checkers return False on success, True on failure
+    def check_rc_deltas(deltas):
+        return any(deltas)
+    def check_alloc_deltas(deltas):
+        # At least 1/3rd of 0s
+        if 3 * deltas.count(0) < len(deltas):
+            return True
+        # Nothing else than 1s, 0s and -1s
+        if not set(deltas) <= {1,0,-1}:
+            return True
+        return False
+    failed = False
+    for deltas, item_name, checker in [
+        (rc_deltas, 'references', check_rc_deltas),
+        (alloc_deltas, 'memory blocks', check_alloc_deltas)]:
+        if checker(deltas):
+            msg = '%s leaked %s %s, sum=%s' % (
+                test, deltas[nwarmup:], item_name, sum(deltas))
+            print(msg, file=sys.stderr)
+            sys.stderr.flush()
+            with open(fname, "a") as refrep:
+                print(msg, file=refrep)
+                refrep.flush()
+            failed = True
+    return failed
+
+
+def dash_R_cleanup(fs, ps, pic, zdc, abcs):
+    import gc, copyreg
+    import _strptime, linecache
+    import urllib.parse, urllib.request, mimetypes, doctest
+    import struct, filecmp, collections.abc
+    from distutils.dir_util import _path_created
+    from weakref import WeakSet
+
+    # Clear the warnings registry, so they can be displayed again
+    for mod in sys.modules.values():
+        if hasattr(mod, '__warningregistry__'):
+            del mod.__warningregistry__
+
+    # Restore some original values.
+    warnings.filters[:] = fs
+    copyreg.dispatch_table.clear()
+    copyreg.dispatch_table.update(ps)
+    sys.path_importer_cache.clear()
+    sys.path_importer_cache.update(pic)
+    try:
+        import zipimport
+    except ImportError:
+        pass # Run unmodified on platforms without zipimport support
+    else:
+        zipimport._zip_directory_cache.clear()
+        zipimport._zip_directory_cache.update(zdc)
+
+    # clear type cache
+    sys._clear_type_cache()
+
+    # Clear ABC registries, restoring previously saved ABC registries.
+    for abc in [getattr(collections.abc, a) for a in collections.abc.__all__]:
+        if not isabstract(abc):
+            continue
+        for obj in abc.__subclasses__() + [abc]:
+            obj._abc_registry = abcs.get(obj, WeakSet()).copy()
+            obj._abc_cache.clear()
+            obj._abc_negative_cache.clear()
+
+    # Flush standard output, so that buffered data is sent to the OS and
+    # associated Python objects are reclaimed.
+    for stream in (sys.stdout, sys.stderr, sys.__stdout__, sys.__stderr__):
+        if stream is not None:
+            stream.flush()
+
+    # Clear assorted module caches.
+    _path_created.clear()
+    re.purge()
+    _strptime._regex_cache.clear()
+    urllib.parse.clear_cache()
+    urllib.request.urlcleanup()
+    linecache.clearcache()
+    mimetypes._default_mime_types()
+    filecmp._cache.clear()
+    struct._clearcache()
+    doctest.master = None
+    try:
+        import ctypes
+    except ImportError:
+        # Don't worry about resetting the cache if ctypes is not supported
+        pass
+    else:
+        ctypes._reset_cache()
+
+    # Collect cyclic trash and read memory statistics immediately after.
+    func1 = sys.getallocatedblocks
+    func2 = sys.gettotalrefcount
+    gc.collect()
+    return func1(), func2()
+
+
+def warm_caches():
+    # char cache
+    s = bytes(range(256))
+    for i in range(256):
+        s[i:i+1]
+    # unicode cache
+    x = [chr(i) for i in range(256)]
+    # int cache
+    x = list(range(-5, 257))
diff --git a/Lib/test/libregrtest/runtest.py b/Lib/test/libregrtest/runtest.py
new file mode 100644
index 0000000000..d8c0eb2a86
--- /dev/null
+++ b/Lib/test/libregrtest/runtest.py
@@ -0,0 +1,271 @@
+import faulthandler
+import importlib
+import io
+import json
+import os
+import sys
+import time
+import traceback
+import unittest
+from test import support
+from test.libregrtest.refleak import dash_R
+from test.libregrtest.save_env import saved_test_environment
+
+
+# Test result constants.
+PASSED = 1
+FAILED = 0
+ENV_CHANGED = -1
+SKIPPED = -2
+RESOURCE_DENIED = -3
+INTERRUPTED = -4
+CHILD_ERROR = -5   # error in a child process
+
+
+def run_test_in_subprocess(testname, ns):
+    """Run the given test in a subprocess with --slaveargs.
+
+    ns is the option Namespace parsed from command-line arguments. regrtest
+    is invoked in a subprocess with the --slaveargs argument; when the
+    subprocess exits, its return code, stdout and stderr are returned as a
+    3-tuple.
+    """
+    from subprocess import Popen, PIPE
+    base_cmd = ([sys.executable] + support.args_from_interpreter_flags() +
+                ['-X', 'faulthandler', '-m', 'test.regrtest'])
+
+    slaveargs = (
+            (testname, ns.verbose, ns.quiet),
+            dict(huntrleaks=ns.huntrleaks,
+                 use_resources=ns.use_resources,
+                 output_on_failure=ns.verbose3,
+                 timeout=ns.timeout, failfast=ns.failfast,
+                 match_tests=ns.match_tests))
+    # Running the child from the same working directory as regrtest's original
+    # invocation ensures that TEMPDIR for the child is the same when
+    # sysconfig.is_python_build() is true. See issue 15300.
+    popen = Popen(base_cmd + ['--slaveargs', json.dumps(slaveargs)],
+                  stdout=PIPE, stderr=PIPE,
+                  universal_newlines=True,
+                  close_fds=(os.name != 'nt'),
+                  cwd=support.SAVEDCWD)
+    stdout, stderr = popen.communicate()
+    retcode = popen.wait()
+    return retcode, stdout, stderr
+
+
+# small set of tests to determine if we have a basically functioning interpreter
+# (i.e. if any of these fail, then anything else is likely to follow)
+STDTESTS = [
+    'test_grammar',
+    'test_opcodes',
+    'test_dict',
+    'test_builtin',
+    'test_exceptions',
+    'test_types',
+    'test_unittest',
+    'test_doctest',
+    'test_doctest2',
+    'test_support'
+]
+
+# set of tests that we don't want to be executed when using regrtest
+NOTTESTS = set()
+
+
+def findtests(testdir=None, stdtests=STDTESTS, nottests=NOTTESTS):
+    """Return a list of all applicable test modules."""
+    testdir = findtestdir(testdir)
+    names = os.listdir(testdir)
+    tests = []
+    others = set(stdtests) | nottests
+    for name in names:
+        mod, ext = os.path.splitext(name)
+        if mod[:5] == "test_" and ext in (".py", "") and mod not in others:
+            tests.append(mod)
+    return stdtests + sorted(tests)
+
+
+def runtest(test, verbose, quiet,
+            huntrleaks=False, use_resources=None,
+            output_on_failure=False, failfast=False, match_tests=None,
+            timeout=None):
+    """Run a single test.
+
+    test -- the name of the test
+    verbose -- if true, print more messages
+    quiet -- if true, don't print 'skipped' messages (probably redundant)
+    huntrleaks -- run multiple times to test for leaks; requires a debug
+                  build; a triple corresponding to -R's three arguments
+    use_resources -- list of extra resources to use
+    output_on_failure -- if true, display test output on failure
+    timeout -- dump the traceback and exit if a test takes more than
+               timeout seconds
+    failfast, match_tests -- See regrtest command-line flags for these.
+
+    Returns the tuple result, test_time, where result is one of the constants:
+        INTERRUPTED      KeyboardInterrupt when run under -j
+        RESOURCE_DENIED  test skipped because resource denied
+        SKIPPED          test skipped for some other reason
+        ENV_CHANGED      test failed because it changed the execution environment
+        FAILED           test failed
+        PASSED           test passed
+    """
+
+    if use_resources is not None:
+        support.use_resources = use_resources
+    use_timeout = (timeout is not None)
+    if use_timeout:
+        faulthandler.dump_traceback_later(timeout, exit=True)
+    try:
+        support.match_tests = match_tests
+        if failfast:
+            support.failfast = True
+        if output_on_failure:
+            support.verbose = True
+
+            # Reuse the same instance to all calls to runtest(). Some
+            # tests keep a reference to sys.stdout or sys.stderr
+            # (eg. test_argparse).
+            if runtest.stringio is None:
+                stream = io.StringIO()
+                runtest.stringio = stream
+            else:
+                stream = runtest.stringio
+                stream.seek(0)
+                stream.truncate()
+
+            orig_stdout = sys.stdout
+            orig_stderr = sys.stderr
+            try:
+                sys.stdout = stream
+                sys.stderr = stream
+                result = runtest_inner(test, verbose, quiet, huntrleaks,
+                                       display_failure=False)
+                if result[0] == FAILED:
+                    output = stream.getvalue()
+                    orig_stderr.write(output)
+                    orig_stderr.flush()
+            finally:
+                sys.stdout = orig_stdout
+                sys.stderr = orig_stderr
+        else:
+            support.verbose = verbose  # Tell tests to be moderately quiet
+            result = runtest_inner(test, verbose, quiet, huntrleaks,
+                                   display_failure=not verbose)
+        return result
+    finally:
+        if use_timeout:
+            faulthandler.cancel_dump_traceback_later()
+        cleanup_test_droppings(test, verbose)
+runtest.stringio = None
+
+
+def runtest_inner(test, verbose, quiet,
+                  huntrleaks=False, display_failure=True):
+    support.unload(test)
+
+    test_time = 0.0
+    refleak = False  # True if the test leaked references.
+    try:
+        if test.startswith('test.'):
+            abstest = test
+        else:
+            # Always import it from the test package
+            abstest = 'test.' + test
+        with saved_test_environment(test, verbose, quiet) as environment:
+            start_time = time.time()
+            the_module = importlib.import_module(abstest)
+            # If the test has a test_main, that will run the appropriate
+            # tests.  If not, use normal unittest test loading.
+            test_runner = getattr(the_module, "test_main", None)
+            if test_runner is None:
+                def test_runner():
+                    loader = unittest.TestLoader()
+                    tests = loader.loadTestsFromModule(the_module)
+                    for error in loader.errors:
+                        print(error, file=sys.stderr)
+                    if loader.errors:
+                        raise Exception("errors while loading tests")
+                    support.run_unittest(tests)
+            test_runner()
+            if huntrleaks:
+                refleak = dash_R(the_module, test, test_runner, huntrleaks)
+            test_time = time.time() - start_time
+    except support.ResourceDenied as msg:
+        if not quiet:
+            print(test, "skipped --", msg)
+            sys.stdout.flush()
+        return RESOURCE_DENIED, test_time
+    except unittest.SkipTest as msg:
+        if not quiet:
+            print(test, "skipped --", msg)
+            sys.stdout.flush()
+        return SKIPPED, test_time
+    except KeyboardInterrupt:
+        raise
+    except support.TestFailed as msg:
+        if display_failure:
+            print("test", test, "failed --", msg, file=sys.stderr)
+        else:
+            print("test", test, "failed", file=sys.stderr)
+        sys.stderr.flush()
+        return FAILED, test_time
+    except:
+        msg = traceback.format_exc()
+        print("test", test, "crashed --", msg, file=sys.stderr)
+        sys.stderr.flush()
+        return FAILED, test_time
+    else:
+        if refleak:
+            return FAILED, test_time
+        if environment.changed:
+            return ENV_CHANGED, test_time
+        return PASSED, test_time
+
+
+def cleanup_test_droppings(testname, verbose):
+    import shutil
+    import stat
+    import gc
+
+    # First kill any dangling references to open files etc.
+    # This can also issue some ResourceWarnings which would otherwise get
+    # triggered during the following test run, and possibly produce failures.
+    gc.collect()
+
+    # Try to clean up junk commonly left behind.  While tests shouldn't leave
+    # any files or directories behind, when a test fails that can be tedious
+    # for it to arrange.  The consequences can be especially nasty on Windows,
+    # since if a test leaves a file open, it cannot be deleted by name (while
+    # there's nothing we can do about that here either, we can display the
+    # name of the offending test, which is a real help).
+    for name in (support.TESTFN,
+                 "db_home",
+                ):
+        if not os.path.exists(name):
+            continue
+
+        if os.path.isdir(name):
+            kind, nuker = "directory", shutil.rmtree
+        elif os.path.isfile(name):
+            kind, nuker = "file", os.unlink
+        else:
+            raise SystemError("os.path says %r exists but is neither "
+                              "directory nor file" % name)
+
+        if verbose:
+            print("%r left behind %s %r" % (testname, kind, name))
+        try:
+            # if we have chmod, fix possible permissions problems
+            # that might prevent cleanup
+            if (hasattr(os, 'chmod')):
+                os.chmod(name, stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO)
+            nuker(name)
+        except Exception as msg:
+            print(("%r left behind %s %r and it couldn't be "
+                "removed: %s" % (testname, kind, name, msg)), file=sys.stderr)
+
+
+def findtestdir(path=None):
+    return path or os.path.dirname(os.path.dirname(__file__)) or os.curdir
diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
new file mode 100644
index 0000000000..4f6a1aa3b4
--- /dev/null
+++ b/Lib/test/libregrtest/save_env.py
@@ -0,0 +1,284 @@
+import builtins
+import locale
+import logging
+import os
+import shutil
+import sys
+import sysconfig
+import warnings
+from test import support
+try:
+    import threading
+except ImportError:
+    threading = None
+try:
+    import _multiprocessing, multiprocessing.process
+except ImportError:
+    multiprocessing = None
+
+
+# Unit tests are supposed to leave the execution environment unchanged
+# once they complete.  But sometimes tests have bugs, especially when
+# tests fail, and the changes to environment go on to mess up other
+# tests.  This can cause issues with buildbot stability, since tests
+# are run in random order and so problems may appear to come and go.
+# There are a few things we can save and restore to mitigate this, and
+# the following context manager handles this task.
+
+class saved_test_environment:
+    """Save bits of the test environment and restore them at block exit.
+
+        with saved_test_environment(testname, verbose, quiet):
+            #stuff
+
+    Unless quiet is True, a warning is printed to stderr if any of
+    the saved items was changed by the test.  The attribute 'changed'
+    is initially False, but is set to True if a change is detected.
+
+    If verbose is more than 1, the before and after state of changed
+    items is also printed.
+    """
+
+    changed = False
+
+    def __init__(self, testname, verbose=0, quiet=False):
+        self.testname = testname
+        self.verbose = verbose
+        self.quiet = quiet
+
+    # To add things to save and restore, add a name XXX to the resources list
+    # and add corresponding get_XXX/restore_XXX functions.  get_XXX should
+    # return the value to be saved and compared against a second call to the
+    # get function when test execution completes.  restore_XXX should accept
+    # the saved value and restore the resource using it.  It will be called if
+    # and only if a change in the value is detected.
+    #
+    # Note: XXX will have any '.' replaced with '_' characters when determining
+    # the corresponding method names.
+
+    resources = ('sys.argv', 'cwd', 'sys.stdin', 'sys.stdout', 'sys.stderr',
+                 'os.environ', 'sys.path', 'sys.path_hooks', '__import__',
+                 'warnings.filters', 'asyncore.socket_map',
+                 'logging._handlers', 'logging._handlerList', 'sys.gettrace',
+                 'sys.warnoptions',
+                 # multiprocessing.process._cleanup() may release ref
+                 # to a thread, so check processes first.
+                 'multiprocessing.process._dangling', 'threading._dangling',
+                 'sysconfig._CONFIG_VARS', 'sysconfig._INSTALL_SCHEMES',
+                 'files', 'locale', 'warnings.showwarning',
+                )
+
+    def get_sys_argv(self):
+        return id(sys.argv), sys.argv, sys.argv[:]
+    def restore_sys_argv(self, saved_argv):
+        sys.argv = saved_argv[1]
+        sys.argv[:] = saved_argv[2]
+
+    def get_cwd(self):
+        return os.getcwd()
+    def restore_cwd(self, saved_cwd):
+        os.chdir(saved_cwd)
+
+    def get_sys_stdout(self):
+        return sys.stdout
+    def restore_sys_stdout(self, saved_stdout):
+        sys.stdout = saved_stdout
+
+    def get_sys_stderr(self):
+        return sys.stderr
+    def restore_sys_stderr(self, saved_stderr):
+        sys.stderr = saved_stderr
+
+    def get_sys_stdin(self):
+        return sys.stdin
+    def restore_sys_stdin(self, saved_stdin):
+        sys.stdin = saved_stdin
+
+    def get_os_environ(self):
+        return id(os.environ), os.environ, dict(os.environ)
+    def restore_os_environ(self, saved_environ):
+        os.environ = saved_environ[1]
+        os.environ.clear()
+        os.environ.update(saved_environ[2])
+
+    def get_sys_path(self):
+        return id(sys.path), sys.path, sys.path[:]
+    def restore_sys_path(self, saved_path):
+        sys.path = saved_path[1]
+        sys.path[:] = saved_path[2]
+
+    def get_sys_path_hooks(self):
+        return id(sys.path_hooks), sys.path_hooks, sys.path_hooks[:]
+    def restore_sys_path_hooks(self, saved_hooks):
+        sys.path_hooks = saved_hooks[1]
+        sys.path_hooks[:] = saved_hooks[2]
+
+    def get_sys_gettrace(self):
+        return sys.gettrace()
+    def restore_sys_gettrace(self, trace_fxn):
+        sys.settrace(trace_fxn)
+
+    def get___import__(self):
+        return builtins.__import__
+    def restore___import__(self, import_):
+        builtins.__import__ = import_
+
+    def get_warnings_filters(self):
+        return id(warnings.filters), warnings.filters, warnings.filters[:]
+    def restore_warnings_filters(self, saved_filters):
+        warnings.filters = saved_filters[1]
+        warnings.filters[:] = saved_filters[2]
+
+    def get_asyncore_socket_map(self):
+        asyncore = sys.modules.get('asyncore')
+        # XXX Making a copy keeps objects alive until __exit__ gets called.
+        return asyncore and asyncore.socket_map.copy() or {}
+    def restore_asyncore_socket_map(self, saved_map):
+        asyncore = sys.modules.get('asyncore')
+        if asyncore is not None:
+            asyncore.close_all(ignore_all=True)
+            asyncore.socket_map.update(saved_map)
+
+    def get_shutil_archive_formats(self):
+        # we could call get_archives_formats() but that only returns the
+        # registry keys; we want to check the values too (the functions that
+        # are registered)
+        return shutil._ARCHIVE_FORMATS, shutil._ARCHIVE_FORMATS.copy()
+    def restore_shutil_archive_formats(self, saved):
+        shutil._ARCHIVE_FORMATS = saved[0]
+        shutil._ARCHIVE_FORMATS.clear()
+        shutil._ARCHIVE_FORMATS.update(saved[1])
+
+    def get_shutil_unpack_formats(self):
+        return shutil._UNPACK_FORMATS, shutil._UNPACK_FORMATS.copy()
+    def restore_shutil_unpack_formats(self, saved):
+        shutil._UNPACK_FORMATS = saved[0]
+        shutil._UNPACK_FORMATS.clear()
+        shutil._UNPACK_FORMATS.update(saved[1])
+
+    def get_logging__handlers(self):
+        # _handlers is a WeakValueDictionary
+        return id(logging._handlers), logging._handlers, logging._handlers.copy()
+    def restore_logging__handlers(self, saved_handlers):
+        # Can't easily revert the logging state
+        pass
+
+    def get_logging__handlerList(self):
+        # _handlerList is a list of weakrefs to handlers
+        return id(logging._handlerList), logging._handlerList, logging._handlerList[:]
+    def restore_logging__handlerList(self, saved_handlerList):
+        # Can't easily revert the logging state
+        pass
+
+    def get_sys_warnoptions(self):
+        return id(sys.warnoptions), sys.warnoptions, sys.warnoptions[:]
+    def restore_sys_warnoptions(self, saved_options):
+        sys.warnoptions = saved_options[1]
+        sys.warnoptions[:] = saved_options[2]
+
+    # Controlling dangling references to Thread objects can make it easier
+    # to track reference leaks.
+    def get_threading__dangling(self):
+        if not threading:
+            return None
+        # This copies the weakrefs without making any strong reference
+        return threading._dangling.copy()
+    def restore_threading__dangling(self, saved):
+        if not threading:
+            return
+        threading._dangling.clear()
+        threading._dangling.update(saved)
+
+    # Same for Process objects
+    def get_multiprocessing_process__dangling(self):
+        if not multiprocessing:
+            return None
+        # Unjoined process objects can survive after process exits
+        multiprocessing.process._cleanup()
+        # This copies the weakrefs without making any strong reference
+        return multiprocessing.process._dangling.copy()
+    def restore_multiprocessing_process__dangling(self, saved):
+        if not multiprocessing:
+            return
+        multiprocessing.process._dangling.clear()
+        multiprocessing.process._dangling.update(saved)
+
+    def get_sysconfig__CONFIG_VARS(self):
+        # make sure the dict is initialized
+        sysconfig.get_config_var('prefix')
+        return (id(sysconfig._CONFIG_VARS), sysconfig._CONFIG_VARS,
+                dict(sysconfig._CONFIG_VARS))
+    def restore_sysconfig__CONFIG_VARS(self, saved):
+        sysconfig._CONFIG_VARS = saved[1]
+        sysconfig._CONFIG_VARS.clear()
+        sysconfig._CONFIG_VARS.update(saved[2])
+
+    def get_sysconfig__INSTALL_SCHEMES(self):
+        return (id(sysconfig._INSTALL_SCHEMES), sysconfig._INSTALL_SCHEMES,
+                sysconfig._INSTALL_SCHEMES.copy())
+    def restore_sysconfig__INSTALL_SCHEMES(self, saved):
+        sysconfig._INSTALL_SCHEMES = saved[1]
+        sysconfig._INSTALL_SCHEMES.clear()
+        sysconfig._INSTALL_SCHEMES.update(saved[2])
+
+    def get_files(self):
+        return sorted(fn + ('/' if os.path.isdir(fn) else '')
+                      for fn in os.listdir())
+    def restore_files(self, saved_value):
+        fn = support.TESTFN
+        if fn not in saved_value and (fn + '/') not in saved_value:
+            if os.path.isfile(fn):
+                support.unlink(fn)
+            elif os.path.isdir(fn):
+                support.rmtree(fn)
+
+    _lc = [getattr(locale, lc) for lc in dir(locale)
+           if lc.startswith('LC_')]
+    def get_locale(self):
+        pairings = []
+        for lc in self._lc:
+            try:
+                pairings.append((lc, locale.setlocale(lc, None)))
+            except (TypeError, ValueError):
+                continue
+        return pairings
+    def restore_locale(self, saved):
+        for lc, setting in saved:
+            locale.setlocale(lc, setting)
+
+    def get_warnings_showwarning(self):
+        return warnings.showwarning
+    def restore_warnings_showwarning(self, fxn):
+        warnings.showwarning = fxn
+
+    def resource_info(self):
+        for name in self.resources:
+            method_suffix = name.replace('.', '_')
+            get_name = 'get_' + method_suffix
+            restore_name = 'restore_' + method_suffix
+            yield name, getattr(self, get_name), getattr(self, restore_name)
+
+    def __enter__(self):
+        self.saved_values = dict((name, get()) for name, get, restore
+                                                   in self.resource_info())
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        saved_values = self.saved_values
+        del self.saved_values
+        for name, get, restore in self.resource_info():
+            current = get()
+            original = saved_values.pop(name)
+            # Check for changes to the resource's value
+            if current != original:
+                self.changed = True
+                restore(original)
+                if not self.quiet:
+                    print("Warning -- {} was modified by {}".format(
+                                                 name, self.testname),
+                                                 file=sys.stderr)
+                    if self.verbose > 1:
+                        print("  Before: {}\n  After:  {} ".format(
+                                                  original, current),
+                                                  file=sys.stderr)
+        return False
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 51e9e18029..f01cad45a7 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -9,1232 +9,9 @@ Run this script with -h or --help for documentation.
 # We import importlib *ASAP* in order to test #15386
 import importlib
 
-import argparse
-import builtins
-import faulthandler
-import io
-import json
-import locale
-import logging
 import os
-import platform
-import random
-import re
-import shutil
-import signal
 import sys
-import sysconfig
-import tempfile
-import time
-import traceback
-import unittest
-import warnings
-from inspect import isabstract
-
-try:
-    import threading
-except ImportError:
-    threading = None
-try:
-    import _multiprocessing, multiprocessing.process
-except ImportError:
-    multiprocessing = None
-
-from test.libregrtest import _parse_args
-
-
-# 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().
-# These modules are searched first in sys.path[0] (so '' -- the CWD) and if
-# they are found in the CWD their __file__ and __path__ will be relative (this
-# happens before the chdir).  All the modules imported after the chdir, are
-# not found in the CWD, and since the other paths in sys.path[1:] are absolute
-# (site.py absolutize them), the __file__ and __path__ will be absolute too.
-# Therefore it is necessary to absolutize manually the __file__ and __path__ of
-# the packages to prevent later imports to fail when the CWD is different.
-for module in sys.modules.values():
-    if hasattr(module, '__path__'):
-        module.__path__ = [os.path.abspath(path) for path in module.__path__]
-    if hasattr(module, '__file__'):
-        module.__file__ = os.path.abspath(module.__file__)
-
-
-# MacOSX (a.k.a. Darwin) has a default stack size that is too small
-# for deeply recursive regular expressions.  We see this as crashes in
-# the Python test suite when running test_re.py and test_sre.py.  The
-# fix is to set the stack limit to 2048.
-# This approach may also be useful for other Unixy platforms that
-# suffer from small default stack limits.
-if sys.platform == 'darwin':
-    try:
-        import resource
-    except ImportError:
-        pass
-    else:
-        soft, hard = resource.getrlimit(resource.RLIMIT_STACK)
-        newsoft = min(hard, max(soft, 1024*2048))
-        resource.setrlimit(resource.RLIMIT_STACK, (newsoft, hard))
-
-# Test result constants.
-PASSED = 1
-FAILED = 0
-ENV_CHANGED = -1
-SKIPPED = -2
-RESOURCE_DENIED = -3
-INTERRUPTED = -4
-CHILD_ERROR = -5   # error in a child process
-
-from test import support
-
-# When tests are run from the Python build directory, it is best practice
-# to keep the test files in a subfolder.  This eases the cleanup of leftover
-# files using the "make distclean" command.
-if sysconfig.is_python_build():
-    TEMPDIR = os.path.join(sysconfig.get_config_var('srcdir'), 'build')
-else:
-    TEMPDIR = tempfile.gettempdir()
-TEMPDIR = os.path.abspath(TEMPDIR)
-
-def run_test_in_subprocess(testname, ns):
-    """Run the given test in a subprocess with --slaveargs.
-
-    ns is the option Namespace parsed from command-line arguments. regrtest
-    is invoked in a subprocess with the --slaveargs argument; when the
-    subprocess exits, its return code, stdout and stderr are returned as a
-    3-tuple.
-    """
-    from subprocess import Popen, PIPE
-    base_cmd = ([sys.executable] + support.args_from_interpreter_flags() +
-                ['-X', 'faulthandler', '-m', 'test.regrtest'])
-
-    slaveargs = (
-            (testname, ns.verbose, ns.quiet),
-            dict(huntrleaks=ns.huntrleaks,
-                 use_resources=ns.use_resources,
-                 output_on_failure=ns.verbose3,
-                 timeout=ns.timeout, failfast=ns.failfast,
-                 match_tests=ns.match_tests))
-    # Running the child from the same working directory as regrtest's original
-    # invocation ensures that TEMPDIR for the child is the same when
-    # sysconfig.is_python_build() is true. See issue 15300.
-    popen = Popen(base_cmd + ['--slaveargs', json.dumps(slaveargs)],
-                  stdout=PIPE, stderr=PIPE,
-                  universal_newlines=True,
-                  close_fds=(os.name != 'nt'),
-                  cwd=support.SAVEDCWD)
-    stdout, stderr = popen.communicate()
-    retcode = popen.wait()
-    return retcode, stdout, stderr
-
-
-def main(tests=None, **kwargs):
-    """Execute a test suite.
-
-    This also parses command-line options and modifies its behavior
-    accordingly.
-
-    tests -- a list of strings containing test names (optional)
-    testdir -- the directory in which to look for tests (optional)
-
-    Users other than the Python test suite will certainly want to
-    specify testdir; if it's omitted, the directory containing the
-    Python test suite is searched for.
-
-    If the tests argument is omitted, the tests listed on the
-    command-line will be used.  If that's empty, too, then all *.py
-    files beginning with test_ will be used.
-
-    The other default arguments (verbose, quiet, exclude,
-    single, randomize, findleaks, use_resources, trace, coverdir,
-    print_slow, and random_seed) allow programmers calling main()
-    directly to set the values that would normally be set by flags
-    on the command line.
-    """
-    # Display the Python traceback on fatal errors (e.g. segfault)
-    faulthandler.enable(all_threads=True)
-
-    # Display the Python traceback on SIGALRM or SIGUSR1 signal
-    signals = []
-    if hasattr(signal, 'SIGALRM'):
-        signals.append(signal.SIGALRM)
-    if hasattr(signal, 'SIGUSR1'):
-        signals.append(signal.SIGUSR1)
-    for signum in signals:
-        faulthandler.register(signum, chain=True)
-
-    replace_stdout()
-
-    support.record_original_stdout(sys.stdout)
-
-    ns = _parse_args(sys.argv[1:], **kwargs)
-
-    if ns.huntrleaks:
-        # Avoid false positives due to various caches
-        # filling slowly with random data:
-        warm_caches()
-    if ns.memlimit is not None:
-        support.set_memlimit(ns.memlimit)
-    if ns.threshold is not None:
-        import gc
-        gc.set_threshold(ns.threshold)
-    if ns.nowindows:
-        import msvcrt
-        msvcrt.SetErrorMode(msvcrt.SEM_FAILCRITICALERRORS|
-                            msvcrt.SEM_NOALIGNMENTFAULTEXCEPT|
-                            msvcrt.SEM_NOGPFAULTERRORBOX|
-                            msvcrt.SEM_NOOPENFILEERRORBOX)
-        try:
-            msvcrt.CrtSetReportMode
-        except AttributeError:
-            # release build
-            pass
-        else:
-            for m in [msvcrt.CRT_WARN, msvcrt.CRT_ERROR, msvcrt.CRT_ASSERT]:
-                msvcrt.CrtSetReportMode(m, msvcrt.CRTDBG_MODE_FILE)
-                msvcrt.CrtSetReportFile(m, msvcrt.CRTDBG_FILE_STDERR)
-    if ns.wait:
-        input("Press any key to continue...")
-
-    if ns.slaveargs is not None:
-        args, kwargs = json.loads(ns.slaveargs)
-        if kwargs.get('huntrleaks'):
-            unittest.BaseTestSuite._cleanup = False
-        try:
-            result = runtest(*args, **kwargs)
-        except KeyboardInterrupt:
-            result = INTERRUPTED, ''
-        except BaseException as e:
-            traceback.print_exc()
-            result = CHILD_ERROR, str(e)
-        sys.stdout.flush()
-        print()   # Force a newline (just in case)
-        print(json.dumps(result))
-        sys.exit(0)
-
-    good = []
-    bad = []
-    skipped = []
-    resource_denieds = []
-    environment_changed = []
-    interrupted = False
-
-    if ns.findleaks:
-        try:
-            import gc
-        except ImportError:
-            print('No GC available, disabling findleaks.')
-            ns.findleaks = False
-        else:
-            # Uncomment the line below to report garbage that is not
-            # freeable by reference counting alone.  By default only
-            # garbage that is not collectable by the GC is reported.
-            #gc.set_debug(gc.DEBUG_SAVEALL)
-            found_garbage = []
-
-    if ns.huntrleaks:
-        unittest.BaseTestSuite._cleanup = False
-
-    if ns.single:
-        filename = os.path.join(TEMPDIR, 'pynexttest')
-        try:
-            with open(filename, 'r') as fp:
-                next_test = fp.read().strip()
-                tests = [next_test]
-        except OSError:
-            pass
-
-    if ns.fromfile:
-        tests = []
-        with open(os.path.join(support.SAVEDCWD, ns.fromfile)) as fp:
-            count_pat = re.compile(r'\[\s*\d+/\s*\d+\]')
-            for line in fp:
-                line = count_pat.sub('', line)
-                guts = line.split() # assuming no test has whitespace in its name
-                if guts and not guts[0].startswith('#'):
-                    tests.extend(guts)
-
-    # Strip .py extensions.
-    removepy(ns.args)
-    removepy(tests)
-
-    stdtests = STDTESTS[:]
-    nottests = NOTTESTS.copy()
-    if ns.exclude:
-        for arg in ns.args:
-            if arg in stdtests:
-                stdtests.remove(arg)
-            nottests.add(arg)
-        ns.args = []
-
-    # For a partial run, we do not need to clutter the output.
-    if ns.verbose or ns.header or not (ns.quiet or ns.single or tests or ns.args):
-        # Print basic platform information
-        print("==", platform.python_implementation(), *sys.version.split())
-        print("==  ", platform.platform(aliased=True),
-                      "%s-endian" % sys.byteorder)
-        print("==  ", "hash algorithm:", sys.hash_info.algorithm,
-              "64bit" if sys.maxsize > 2**32 else "32bit")
-        print("==  ", os.getcwd())
-        print("Testing with flags:", sys.flags)
-
-    # if testdir is set, then we are not running the python tests suite, so
-    # don't add default tests to be executed or skipped (pass empty values)
-    if ns.testdir:
-        alltests = findtests(ns.testdir, list(), set())
-    else:
-        alltests = findtests(ns.testdir, stdtests, nottests)
-
-    selected = tests or ns.args or alltests
-    if ns.single:
-        selected = selected[:1]
-        try:
-            next_single_test = alltests[alltests.index(selected[0])+1]
-        except IndexError:
-            next_single_test = None
-    # Remove all the selected tests that precede start if it's set.
-    if ns.start:
-        try:
-            del selected[:selected.index(ns.start)]
-        except ValueError:
-            print("Couldn't find starting test (%s), using all tests" % ns.start)
-    if ns.randomize:
-        if ns.random_seed is None:
-            ns.random_seed = random.randrange(10000000)
-        random.seed(ns.random_seed)
-        print("Using random seed", ns.random_seed)
-        random.shuffle(selected)
-    if ns.trace:
-        import trace, tempfile
-        tracer = trace.Trace(ignoredirs=[sys.base_prefix, sys.base_exec_prefix,
-                                         tempfile.gettempdir()],
-                             trace=False, count=True)
-
-    test_times = []
-    support.verbose = ns.verbose      # Tell tests to be moderately quiet
-    support.use_resources = ns.use_resources
-    save_modules = sys.modules.keys()
-
-    def accumulate_result(test, result):
-        ok, test_time = result
-        test_times.append((test_time, test))
-        if ok == PASSED:
-            good.append(test)
-        elif ok == FAILED:
-            bad.append(test)
-        elif ok == ENV_CHANGED:
-            environment_changed.append(test)
-        elif ok == SKIPPED:
-            skipped.append(test)
-        elif ok == RESOURCE_DENIED:
-            skipped.append(test)
-            resource_denieds.append(test)
-
-    if ns.forever:
-        def test_forever(tests=list(selected)):
-            while True:
-                for test in tests:
-                    yield test
-                    if bad:
-                        return
-        tests = test_forever()
-        test_count = ''
-        test_count_width = 3
-    else:
-        tests = iter(selected)
-        test_count = '/{}'.format(len(selected))
-        test_count_width = len(test_count) - 1
-
-    if ns.use_mp:
-        try:
-            from threading import Thread
-        except ImportError:
-            print("Multiprocess option requires thread support")
-            sys.exit(2)
-        from queue import Queue
-        debug_output_pat = re.compile(r"\[\d+ refs, \d+ blocks\]$")
-        output = Queue()
-        pending = MultiprocessTests(tests)
-        def work():
-            # A worker thread.
-            try:
-                while True:
-                    try:
-                        test = next(pending)
-                    except StopIteration:
-                        output.put((None, None, None, None))
-                        return
-                    retcode, stdout, stderr = run_test_in_subprocess(test, ns)
-                    # Strip last refcount output line if it exists, since it
-                    # comes from the shutdown of the interpreter in the subcommand.
-                    stderr = debug_output_pat.sub("", stderr)
-                    stdout, _, result = stdout.strip().rpartition("\n")
-                    if retcode != 0:
-                        result = (CHILD_ERROR, "Exit code %s" % retcode)
-                        output.put((test, stdout.rstrip(), stderr.rstrip(), result))
-                        return
-                    if not result:
-                        output.put((None, None, None, None))
-                        return
-                    result = json.loads(result)
-                    output.put((test, stdout.rstrip(), stderr.rstrip(), result))
-            except BaseException:
-                output.put((None, None, None, None))
-                raise
-        workers = [Thread(target=work) for i in range(ns.use_mp)]
-        for worker in workers:
-            worker.start()
-        finished = 0
-        test_index = 1
-        try:
-            while finished < ns.use_mp:
-                test, stdout, stderr, result = output.get()
-                if test is None:
-                    finished += 1
-                    continue
-                accumulate_result(test, result)
-                if not ns.quiet:
-                    fmt = "[{1:{0}}{2}/{3}] {4}" if bad else "[{1:{0}}{2}] {4}"
-                    print(fmt.format(
-                        test_count_width, test_index, test_count,
-                        len(bad), test))
-                if stdout:
-                    print(stdout)
-                if stderr:
-                    print(stderr, file=sys.stderr)
-                sys.stdout.flush()
-                sys.stderr.flush()
-                if result[0] == INTERRUPTED:
-                    raise KeyboardInterrupt
-                if result[0] == CHILD_ERROR:
-                    raise Exception("Child error on {}: {}".format(test, result[1]))
-                test_index += 1
-        except KeyboardInterrupt:
-            interrupted = True
-            pending.interrupted = True
-        for worker in workers:
-            worker.join()
-    else:
-        for test_index, test in enumerate(tests, 1):
-            if not ns.quiet:
-                fmt = "[{1:{0}}{2}/{3}] {4}" if bad else "[{1:{0}}{2}] {4}"
-                print(fmt.format(
-                    test_count_width, test_index, test_count, len(bad), test))
-                sys.stdout.flush()
-            if ns.trace:
-                # If we're tracing code coverage, then we don't exit with status
-                # if on a false return value from main.
-                tracer.runctx('runtest(test, ns.verbose, ns.quiet, timeout=ns.timeout)',
-                              globals=globals(), locals=vars())
-            else:
-                try:
-                    result = runtest(test, ns.verbose, ns.quiet,
-                                     ns.huntrleaks,
-                                     output_on_failure=ns.verbose3,
-                                     timeout=ns.timeout, failfast=ns.failfast,
-                                     match_tests=ns.match_tests)
-                    accumulate_result(test, result)
-                except KeyboardInterrupt:
-                    interrupted = True
-                    break
-            if ns.findleaks:
-                gc.collect()
-                if gc.garbage:
-                    print("Warning: test created", len(gc.garbage), end=' ')
-                    print("uncollectable object(s).")
-                    # move the uncollectable objects somewhere so we don't see
-                    # them again
-                    found_garbage.extend(gc.garbage)
-                    del gc.garbage[:]
-            # Unload the newly imported modules (best effort finalization)
-            for module in sys.modules.keys():
-                if module not in save_modules and module.startswith("test."):
-                    support.unload(module)
-
-    if interrupted:
-        # print a newline after ^C
-        print()
-        print("Test suite interrupted by signal SIGINT.")
-        omitted = set(selected) - set(good) - set(bad) - set(skipped)
-        print(count(len(omitted), "test"), "omitted:")
-        printlist(omitted)
-    if good and not ns.quiet:
-        if not bad and not skipped and not interrupted and len(good) > 1:
-            print("All", end=' ')
-        print(count(len(good), "test"), "OK.")
-    if ns.print_slow:
-        test_times.sort(reverse=True)
-        print("10 slowest tests:")
-        for time, test in test_times[:10]:
-            print("%s: %.1fs" % (test, time))
-    if bad:
-        print(count(len(bad), "test"), "failed:")
-        printlist(bad)
-    if environment_changed:
-        print("{} altered the execution environment:".format(
-                 count(len(environment_changed), "test")))
-        printlist(environment_changed)
-    if skipped and not ns.quiet:
-        print(count(len(skipped), "test"), "skipped:")
-        printlist(skipped)
-
-    if ns.verbose2 and bad:
-        print("Re-running failed tests in verbose mode")
-        for test in bad[:]:
-            print("Re-running test %r in verbose mode" % test)
-            sys.stdout.flush()
-            try:
-                ns.verbose = True
-                ok = runtest(test, True, ns.quiet, ns.huntrleaks,
-                             timeout=ns.timeout)
-            except KeyboardInterrupt:
-                # print a newline separate from the ^C
-                print()
-                break
-            else:
-                if ok[0] in {PASSED, ENV_CHANGED, SKIPPED, RESOURCE_DENIED}:
-                    bad.remove(test)
-        else:
-            if bad:
-                print(count(len(bad), 'test'), "failed again:")
-                printlist(bad)
-
-    if ns.single:
-        if next_single_test:
-            with open(filename, 'w') as fp:
-                fp.write(next_single_test + '\n')
-        else:
-            os.unlink(filename)
-
-    if ns.trace:
-        r = tracer.results()
-        r.write_results(show_missing=True, summary=True, coverdir=ns.coverdir)
-
-    if ns.runleaks:
-        os.system("leaks %d" % os.getpid())
-
-    sys.exit(len(bad) > 0 or interrupted)
-
-
-# small set of tests to determine if we have a basically functioning interpreter
-# (i.e. if any of these fail, then anything else is likely to follow)
-STDTESTS = [
-    'test_grammar',
-    'test_opcodes',
-    'test_dict',
-    'test_builtin',
-    'test_exceptions',
-    'test_types',
-    'test_unittest',
-    'test_doctest',
-    'test_doctest2',
-    'test_support'
-]
-
-# set of tests that we don't want to be executed when using regrtest
-NOTTESTS = set()
-
-def findtests(testdir=None, stdtests=STDTESTS, nottests=NOTTESTS):
-    """Return a list of all applicable test modules."""
-    testdir = findtestdir(testdir)
-    names = os.listdir(testdir)
-    tests = []
-    others = set(stdtests) | nottests
-    for name in names:
-        mod, ext = os.path.splitext(name)
-        if mod[:5] == "test_" and ext in (".py", "") and mod not in others:
-            tests.append(mod)
-    return stdtests + sorted(tests)
-
-# We do not use a generator so multiple threads can call next().
-class MultiprocessTests(object):
-
-    """A thread-safe iterator over tests for multiprocess mode."""
-
-    def __init__(self, tests):
-        self.interrupted = False
-        self.lock = threading.Lock()
-        self.tests = tests
-
-    def __iter__(self):
-        return self
-
-    def __next__(self):
-        with self.lock:
-            if self.interrupted:
-                raise StopIteration('tests interrupted')
-            return next(self.tests)
-
-def replace_stdout():
-    """Set stdout encoder error handler to backslashreplace (as stderr error
-    handler) to avoid UnicodeEncodeError when printing a traceback"""
-    import atexit
-
-    stdout = sys.stdout
-    sys.stdout = open(stdout.fileno(), 'w',
-        encoding=stdout.encoding,
-        errors="backslashreplace",
-        closefd=False,
-        newline='\n')
-
-    def restore_stdout():
-        sys.stdout.close()
-        sys.stdout = stdout
-    atexit.register(restore_stdout)
-
-def runtest(test, verbose, quiet,
-            huntrleaks=False, use_resources=None,
-            output_on_failure=False, failfast=False, match_tests=None,
-            timeout=None):
-    """Run a single test.
-
-    test -- the name of the test
-    verbose -- if true, print more messages
-    quiet -- if true, don't print 'skipped' messages (probably redundant)
-    huntrleaks -- run multiple times to test for leaks; requires a debug
-                  build; a triple corresponding to -R's three arguments
-    use_resources -- list of extra resources to use
-    output_on_failure -- if true, display test output on failure
-    timeout -- dump the traceback and exit if a test takes more than
-               timeout seconds
-    failfast, match_tests -- See regrtest command-line flags for these.
-
-    Returns the tuple result, test_time, where result is one of the constants:
-        INTERRUPTED      KeyboardInterrupt when run under -j
-        RESOURCE_DENIED  test skipped because resource denied
-        SKIPPED          test skipped for some other reason
-        ENV_CHANGED      test failed because it changed the execution environment
-        FAILED           test failed
-        PASSED           test passed
-    """
-
-    if use_resources is not None:
-        support.use_resources = use_resources
-    use_timeout = (timeout is not None)
-    if use_timeout:
-        faulthandler.dump_traceback_later(timeout, exit=True)
-    try:
-        support.match_tests = match_tests
-        if failfast:
-            support.failfast = True
-        if output_on_failure:
-            support.verbose = True
-
-            # Reuse the same instance to all calls to runtest(). Some
-            # tests keep a reference to sys.stdout or sys.stderr
-            # (eg. test_argparse).
-            if runtest.stringio is None:
-                stream = io.StringIO()
-                runtest.stringio = stream
-            else:
-                stream = runtest.stringio
-                stream.seek(0)
-                stream.truncate()
-
-            orig_stdout = sys.stdout
-            orig_stderr = sys.stderr
-            try:
-                sys.stdout = stream
-                sys.stderr = stream
-                result = runtest_inner(test, verbose, quiet, huntrleaks,
-                                       display_failure=False)
-                if result[0] == FAILED:
-                    output = stream.getvalue()
-                    orig_stderr.write(output)
-                    orig_stderr.flush()
-            finally:
-                sys.stdout = orig_stdout
-                sys.stderr = orig_stderr
-        else:
-            support.verbose = verbose  # Tell tests to be moderately quiet
-            result = runtest_inner(test, verbose, quiet, huntrleaks,
-                                   display_failure=not verbose)
-        return result
-    finally:
-        if use_timeout:
-            faulthandler.cancel_dump_traceback_later()
-        cleanup_test_droppings(test, verbose)
-runtest.stringio = None
-
-# Unit tests are supposed to leave the execution environment unchanged
-# once they complete.  But sometimes tests have bugs, especially when
-# tests fail, and the changes to environment go on to mess up other
-# tests.  This can cause issues with buildbot stability, since tests
-# are run in random order and so problems may appear to come and go.
-# There are a few things we can save and restore to mitigate this, and
-# the following context manager handles this task.
-
-class saved_test_environment:
-    """Save bits of the test environment and restore them at block exit.
-
-        with saved_test_environment(testname, verbose, quiet):
-            #stuff
-
-    Unless quiet is True, a warning is printed to stderr if any of
-    the saved items was changed by the test.  The attribute 'changed'
-    is initially False, but is set to True if a change is detected.
-
-    If verbose is more than 1, the before and after state of changed
-    items is also printed.
-    """
-
-    changed = False
-
-    def __init__(self, testname, verbose=0, quiet=False):
-        self.testname = testname
-        self.verbose = verbose
-        self.quiet = quiet
-
-    # To add things to save and restore, add a name XXX to the resources list
-    # and add corresponding get_XXX/restore_XXX functions.  get_XXX should
-    # return the value to be saved and compared against a second call to the
-    # get function when test execution completes.  restore_XXX should accept
-    # the saved value and restore the resource using it.  It will be called if
-    # and only if a change in the value is detected.
-    #
-    # Note: XXX will have any '.' replaced with '_' characters when determining
-    # the corresponding method names.
-
-    resources = ('sys.argv', 'cwd', 'sys.stdin', 'sys.stdout', 'sys.stderr',
-                 'os.environ', 'sys.path', 'sys.path_hooks', '__import__',
-                 'warnings.filters', 'asyncore.socket_map',
-                 'logging._handlers', 'logging._handlerList', 'sys.gettrace',
-                 'sys.warnoptions',
-                 # multiprocessing.process._cleanup() may release ref
-                 # to a thread, so check processes first.
-                 'multiprocessing.process._dangling', 'threading._dangling',
-                 'sysconfig._CONFIG_VARS', 'sysconfig._INSTALL_SCHEMES',
-                 'files', 'locale', 'warnings.showwarning',
-                )
-
-    def get_sys_argv(self):
-        return id(sys.argv), sys.argv, sys.argv[:]
-    def restore_sys_argv(self, saved_argv):
-        sys.argv = saved_argv[1]
-        sys.argv[:] = saved_argv[2]
-
-    def get_cwd(self):
-        return os.getcwd()
-    def restore_cwd(self, saved_cwd):
-        os.chdir(saved_cwd)
-
-    def get_sys_stdout(self):
-        return sys.stdout
-    def restore_sys_stdout(self, saved_stdout):
-        sys.stdout = saved_stdout
-
-    def get_sys_stderr(self):
-        return sys.stderr
-    def restore_sys_stderr(self, saved_stderr):
-        sys.stderr = saved_stderr
-
-    def get_sys_stdin(self):
-        return sys.stdin
-    def restore_sys_stdin(self, saved_stdin):
-        sys.stdin = saved_stdin
-
-    def get_os_environ(self):
-        return id(os.environ), os.environ, dict(os.environ)
-    def restore_os_environ(self, saved_environ):
-        os.environ = saved_environ[1]
-        os.environ.clear()
-        os.environ.update(saved_environ[2])
-
-    def get_sys_path(self):
-        return id(sys.path), sys.path, sys.path[:]
-    def restore_sys_path(self, saved_path):
-        sys.path = saved_path[1]
-        sys.path[:] = saved_path[2]
-
-    def get_sys_path_hooks(self):
-        return id(sys.path_hooks), sys.path_hooks, sys.path_hooks[:]
-    def restore_sys_path_hooks(self, saved_hooks):
-        sys.path_hooks = saved_hooks[1]
-        sys.path_hooks[:] = saved_hooks[2]
-
-    def get_sys_gettrace(self):
-        return sys.gettrace()
-    def restore_sys_gettrace(self, trace_fxn):
-        sys.settrace(trace_fxn)
-
-    def get___import__(self):
-        return builtins.__import__
-    def restore___import__(self, import_):
-        builtins.__import__ = import_
-
-    def get_warnings_filters(self):
-        return id(warnings.filters), warnings.filters, warnings.filters[:]
-    def restore_warnings_filters(self, saved_filters):
-        warnings.filters = saved_filters[1]
-        warnings.filters[:] = saved_filters[2]
-
-    def get_asyncore_socket_map(self):
-        asyncore = sys.modules.get('asyncore')
-        # XXX Making a copy keeps objects alive until __exit__ gets called.
-        return asyncore and asyncore.socket_map.copy() or {}
-    def restore_asyncore_socket_map(self, saved_map):
-        asyncore = sys.modules.get('asyncore')
-        if asyncore is not None:
-            asyncore.close_all(ignore_all=True)
-            asyncore.socket_map.update(saved_map)
-
-    def get_shutil_archive_formats(self):
-        # we could call get_archives_formats() but that only returns the
-        # registry keys; we want to check the values too (the functions that
-        # are registered)
-        return shutil._ARCHIVE_FORMATS, shutil._ARCHIVE_FORMATS.copy()
-    def restore_shutil_archive_formats(self, saved):
-        shutil._ARCHIVE_FORMATS = saved[0]
-        shutil._ARCHIVE_FORMATS.clear()
-        shutil._ARCHIVE_FORMATS.update(saved[1])
-
-    def get_shutil_unpack_formats(self):
-        return shutil._UNPACK_FORMATS, shutil._UNPACK_FORMATS.copy()
-    def restore_shutil_unpack_formats(self, saved):
-        shutil._UNPACK_FORMATS = saved[0]
-        shutil._UNPACK_FORMATS.clear()
-        shutil._UNPACK_FORMATS.update(saved[1])
-
-    def get_logging__handlers(self):
-        # _handlers is a WeakValueDictionary
-        return id(logging._handlers), logging._handlers, logging._handlers.copy()
-    def restore_logging__handlers(self, saved_handlers):
-        # Can't easily revert the logging state
-        pass
-
-    def get_logging__handlerList(self):
-        # _handlerList is a list of weakrefs to handlers
-        return id(logging._handlerList), logging._handlerList, logging._handlerList[:]
-    def restore_logging__handlerList(self, saved_handlerList):
-        # Can't easily revert the logging state
-        pass
-
-    def get_sys_warnoptions(self):
-        return id(sys.warnoptions), sys.warnoptions, sys.warnoptions[:]
-    def restore_sys_warnoptions(self, saved_options):
-        sys.warnoptions = saved_options[1]
-        sys.warnoptions[:] = saved_options[2]
-
-    # Controlling dangling references to Thread objects can make it easier
-    # to track reference leaks.
-    def get_threading__dangling(self):
-        if not threading:
-            return None
-        # This copies the weakrefs without making any strong reference
-        return threading._dangling.copy()
-    def restore_threading__dangling(self, saved):
-        if not threading:
-            return
-        threading._dangling.clear()
-        threading._dangling.update(saved)
-
-    # Same for Process objects
-    def get_multiprocessing_process__dangling(self):
-        if not multiprocessing:
-            return None
-        # Unjoined process objects can survive after process exits
-        multiprocessing.process._cleanup()
-        # This copies the weakrefs without making any strong reference
-        return multiprocessing.process._dangling.copy()
-    def restore_multiprocessing_process__dangling(self, saved):
-        if not multiprocessing:
-            return
-        multiprocessing.process._dangling.clear()
-        multiprocessing.process._dangling.update(saved)
-
-    def get_sysconfig__CONFIG_VARS(self):
-        # make sure the dict is initialized
-        sysconfig.get_config_var('prefix')
-        return (id(sysconfig._CONFIG_VARS), sysconfig._CONFIG_VARS,
-                dict(sysconfig._CONFIG_VARS))
-    def restore_sysconfig__CONFIG_VARS(self, saved):
-        sysconfig._CONFIG_VARS = saved[1]
-        sysconfig._CONFIG_VARS.clear()
-        sysconfig._CONFIG_VARS.update(saved[2])
-
-    def get_sysconfig__INSTALL_SCHEMES(self):
-        return (id(sysconfig._INSTALL_SCHEMES), sysconfig._INSTALL_SCHEMES,
-                sysconfig._INSTALL_SCHEMES.copy())
-    def restore_sysconfig__INSTALL_SCHEMES(self, saved):
-        sysconfig._INSTALL_SCHEMES = saved[1]
-        sysconfig._INSTALL_SCHEMES.clear()
-        sysconfig._INSTALL_SCHEMES.update(saved[2])
-
-    def get_files(self):
-        return sorted(fn + ('/' if os.path.isdir(fn) else '')
-                      for fn in os.listdir())
-    def restore_files(self, saved_value):
-        fn = support.TESTFN
-        if fn not in saved_value and (fn + '/') not in saved_value:
-            if os.path.isfile(fn):
-                support.unlink(fn)
-            elif os.path.isdir(fn):
-                support.rmtree(fn)
-
-    _lc = [getattr(locale, lc) for lc in dir(locale)
-           if lc.startswith('LC_')]
-    def get_locale(self):
-        pairings = []
-        for lc in self._lc:
-            try:
-                pairings.append((lc, locale.setlocale(lc, None)))
-            except (TypeError, ValueError):
-                continue
-        return pairings
-    def restore_locale(self, saved):
-        for lc, setting in saved:
-            locale.setlocale(lc, setting)
-
-    def get_warnings_showwarning(self):
-        return warnings.showwarning
-    def restore_warnings_showwarning(self, fxn):
-        warnings.showwarning = fxn
-
-    def resource_info(self):
-        for name in self.resources:
-            method_suffix = name.replace('.', '_')
-            get_name = 'get_' + method_suffix
-            restore_name = 'restore_' + method_suffix
-            yield name, getattr(self, get_name), getattr(self, restore_name)
-
-    def __enter__(self):
-        self.saved_values = dict((name, get()) for name, get, restore
-                                                   in self.resource_info())
-        return self
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        saved_values = self.saved_values
-        del self.saved_values
-        for name, get, restore in self.resource_info():
-            current = get()
-            original = saved_values.pop(name)
-            # Check for changes to the resource's value
-            if current != original:
-                self.changed = True
-                restore(original)
-                if not self.quiet:
-                    print("Warning -- {} was modified by {}".format(
-                                                 name, self.testname),
-                                                 file=sys.stderr)
-                    if self.verbose > 1:
-                        print("  Before: {}\n  After:  {} ".format(
-                                                  original, current),
-                                                  file=sys.stderr)
-        return False
-
-
-def runtest_inner(test, verbose, quiet,
-                  huntrleaks=False, display_failure=True):
-    support.unload(test)
-
-    test_time = 0.0
-    refleak = False  # True if the test leaked references.
-    try:
-        if test.startswith('test.'):
-            abstest = test
-        else:
-            # Always import it from the test package
-            abstest = 'test.' + test
-        with saved_test_environment(test, verbose, quiet) as environment:
-            start_time = time.time()
-            the_module = importlib.import_module(abstest)
-            # If the test has a test_main, that will run the appropriate
-            # tests.  If not, use normal unittest test loading.
-            test_runner = getattr(the_module, "test_main", None)
-            if test_runner is None:
-                def test_runner():
-                    loader = unittest.TestLoader()
-                    tests = loader.loadTestsFromModule(the_module)
-                    for error in loader.errors:
-                        print(error, file=sys.stderr)
-                    if loader.errors:
-                        raise Exception("errors while loading tests")
-                    support.run_unittest(tests)
-            test_runner()
-            if huntrleaks:
-                refleak = dash_R(the_module, test, test_runner, huntrleaks)
-            test_time = time.time() - start_time
-    except support.ResourceDenied as msg:
-        if not quiet:
-            print(test, "skipped --", msg)
-            sys.stdout.flush()
-        return RESOURCE_DENIED, test_time
-    except unittest.SkipTest as msg:
-        if not quiet:
-            print(test, "skipped --", msg)
-            sys.stdout.flush()
-        return SKIPPED, test_time
-    except KeyboardInterrupt:
-        raise
-    except support.TestFailed as msg:
-        if display_failure:
-            print("test", test, "failed --", msg, file=sys.stderr)
-        else:
-            print("test", test, "failed", file=sys.stderr)
-        sys.stderr.flush()
-        return FAILED, test_time
-    except:
-        msg = traceback.format_exc()
-        print("test", test, "crashed --", msg, file=sys.stderr)
-        sys.stderr.flush()
-        return FAILED, test_time
-    else:
-        if refleak:
-            return FAILED, test_time
-        if environment.changed:
-            return ENV_CHANGED, test_time
-        return PASSED, test_time
-
-def cleanup_test_droppings(testname, verbose):
-    import shutil
-    import stat
-    import gc
-
-    # First kill any dangling references to open files etc.
-    # This can also issue some ResourceWarnings which would otherwise get
-    # triggered during the following test run, and possibly produce failures.
-    gc.collect()
-
-    # Try to clean up junk commonly left behind.  While tests shouldn't leave
-    # any files or directories behind, when a test fails that can be tedious
-    # for it to arrange.  The consequences can be especially nasty on Windows,
-    # since if a test leaves a file open, it cannot be deleted by name (while
-    # there's nothing we can do about that here either, we can display the
-    # name of the offending test, which is a real help).
-    for name in (support.TESTFN,
-                 "db_home",
-                ):
-        if not os.path.exists(name):
-            continue
-
-        if os.path.isdir(name):
-            kind, nuker = "directory", shutil.rmtree
-        elif os.path.isfile(name):
-            kind, nuker = "file", os.unlink
-        else:
-            raise SystemError("os.path says %r exists but is neither "
-                              "directory nor file" % name)
-
-        if verbose:
-            print("%r left behind %s %r" % (testname, kind, name))
-        try:
-            # if we have chmod, fix possible permissions problems
-            # that might prevent cleanup
-            if (hasattr(os, 'chmod')):
-                os.chmod(name, stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO)
-            nuker(name)
-        except Exception as msg:
-            print(("%r left behind %s %r and it couldn't be "
-                "removed: %s" % (testname, kind, name, msg)), file=sys.stderr)
-
-def dash_R(the_module, test, indirect_test, huntrleaks):
-    """Run a test multiple times, looking for reference leaks.
-
-    Returns:
-        False if the test didn't leak references; True if we detected refleaks.
-    """
-    # This code is hackish and inelegant, but it seems to do the job.
-    import copyreg
-    import collections.abc
-
-    if not hasattr(sys, 'gettotalrefcount'):
-        raise Exception("Tracking reference leaks requires a debug build "
-                        "of Python")
-
-    # Save current values for dash_R_cleanup() to restore.
-    fs = warnings.filters[:]
-    ps = copyreg.dispatch_table.copy()
-    pic = sys.path_importer_cache.copy()
-    try:
-        import zipimport
-    except ImportError:
-        zdc = None # Run unmodified on platforms without zipimport support
-    else:
-        zdc = zipimport._zip_directory_cache.copy()
-    abcs = {}
-    for abc in [getattr(collections.abc, a) for a in collections.abc.__all__]:
-        if not isabstract(abc):
-            continue
-        for obj in abc.__subclasses__() + [abc]:
-            abcs[obj] = obj._abc_registry.copy()
-
-    nwarmup, ntracked, fname = huntrleaks
-    fname = os.path.join(support.SAVEDCWD, fname)
-    repcount = nwarmup + ntracked
-    rc_deltas = [0] * repcount
-    alloc_deltas = [0] * repcount
-
-    print("beginning", repcount, "repetitions", file=sys.stderr)
-    print(("1234567890"*(repcount//10 + 1))[:repcount], file=sys.stderr)
-    sys.stderr.flush()
-    for i in range(repcount):
-        indirect_test()
-        alloc_after, rc_after = dash_R_cleanup(fs, ps, pic, zdc, abcs)
-        sys.stderr.write('.')
-        sys.stderr.flush()
-        if i >= nwarmup:
-            rc_deltas[i] = rc_after - rc_before
-            alloc_deltas[i] = alloc_after - alloc_before
-        alloc_before, rc_before = alloc_after, rc_after
-    print(file=sys.stderr)
-    # These checkers return False on success, True on failure
-    def check_rc_deltas(deltas):
-        return any(deltas)
-    def check_alloc_deltas(deltas):
-        # At least 1/3rd of 0s
-        if 3 * deltas.count(0) < len(deltas):
-            return True
-        # Nothing else than 1s, 0s and -1s
-        if not set(deltas) <= {1,0,-1}:
-            return True
-        return False
-    failed = False
-    for deltas, item_name, checker in [
-        (rc_deltas, 'references', check_rc_deltas),
-        (alloc_deltas, 'memory blocks', check_alloc_deltas)]:
-        if checker(deltas):
-            msg = '%s leaked %s %s, sum=%s' % (
-                test, deltas[nwarmup:], item_name, sum(deltas))
-            print(msg, file=sys.stderr)
-            sys.stderr.flush()
-            with open(fname, "a") as refrep:
-                print(msg, file=refrep)
-                refrep.flush()
-            failed = True
-    return failed
-
-def dash_R_cleanup(fs, ps, pic, zdc, abcs):
-    import gc, copyreg
-    import _strptime, linecache
-    import urllib.parse, urllib.request, mimetypes, doctest
-    import struct, filecmp, collections.abc
-    from distutils.dir_util import _path_created
-    from weakref import WeakSet
-
-    # Clear the warnings registry, so they can be displayed again
-    for mod in sys.modules.values():
-        if hasattr(mod, '__warningregistry__'):
-            del mod.__warningregistry__
-
-    # Restore some original values.
-    warnings.filters[:] = fs
-    copyreg.dispatch_table.clear()
-    copyreg.dispatch_table.update(ps)
-    sys.path_importer_cache.clear()
-    sys.path_importer_cache.update(pic)
-    try:
-        import zipimport
-    except ImportError:
-        pass # Run unmodified on platforms without zipimport support
-    else:
-        zipimport._zip_directory_cache.clear()
-        zipimport._zip_directory_cache.update(zdc)
-
-    # clear type cache
-    sys._clear_type_cache()
-
-    # Clear ABC registries, restoring previously saved ABC registries.
-    for abc in [getattr(collections.abc, a) for a in collections.abc.__all__]:
-        if not isabstract(abc):
-            continue
-        for obj in abc.__subclasses__() + [abc]:
-            obj._abc_registry = abcs.get(obj, WeakSet()).copy()
-            obj._abc_cache.clear()
-            obj._abc_negative_cache.clear()
-
-    # Flush standard output, so that buffered data is sent to the OS and
-    # associated Python objects are reclaimed.
-    for stream in (sys.stdout, sys.stderr, sys.__stdout__, sys.__stderr__):
-        if stream is not None:
-            stream.flush()
-
-    # Clear assorted module caches.
-    _path_created.clear()
-    re.purge()
-    _strptime._regex_cache.clear()
-    urllib.parse.clear_cache()
-    urllib.request.urlcleanup()
-    linecache.clearcache()
-    mimetypes._default_mime_types()
-    filecmp._cache.clear()
-    struct._clearcache()
-    doctest.master = None
-    try:
-        import ctypes
-    except ImportError:
-        # Don't worry about resetting the cache if ctypes is not supported
-        pass
-    else:
-        ctypes._reset_cache()
-
-    # Collect cyclic trash and read memory statistics immediately after.
-    func1 = sys.getallocatedblocks
-    func2 = sys.gettotalrefcount
-    gc.collect()
-    return func1(), func2()
-
-def warm_caches():
-    # char cache
-    s = bytes(range(256))
-    for i in range(256):
-        s[i:i+1]
-    # unicode cache
-    x = [chr(i) for i in range(256)]
-    # int cache
-    x = list(range(-5, 257))
-
-def findtestdir(path=None):
-    return path or os.path.dirname(__file__) or os.curdir
-
-def removepy(names):
-    if not names:
-        return
-    for idx, name in enumerate(names):
-        basename, ext = os.path.splitext(name)
-        if ext == '.py':
-            names[idx] = basename
-
-def count(n, word):
-    if n == 1:
-        return "%d %s" % (n, word)
-    else:
-        return "%d %ss" % (n, word)
-
-def printlist(x, width=70, indent=4):
-    """Print the elements of iterable x to stdout.
-
-    Optional arg width (default 70) is the maximum line length.
-    Optional arg indent (default 4) is the number of blanks with which to
-    begin each line.
-    """
-
-    from textwrap import fill
-    blanks = ' ' * indent
-    # Print the sorted list: 'x' may be a '--random' list or a set()
-    print(fill(' '.join(str(elt) for elt in sorted(x)), width,
-               initial_indent=blanks, subsequent_indent=blanks))
-
-
-def main_in_temp_cwd():
-    """Run main() in a temporary working directory."""
-    if sysconfig.is_python_build():
-        try:
-            os.mkdir(TEMPDIR)
-        except FileExistsError:
-            pass
-
-    # Define a writable temp dir that will be used as cwd while running
-    # the tests. The name of the dir includes the pid to allow parallel
-    # testing (see the -j option).
-    test_cwd = 'test_python_{}'.format(os.getpid())
-    test_cwd = os.path.join(TEMPDIR, test_cwd)
-
-    # Run the tests in a context manager that temporarily changes the CWD to a
-    # temporary and writable directory.  If it's not possible to create or
-    # change the CWD, the original CWD will be used.  The original CWD is
-    # available from support.SAVEDCWD.
-    with support.temp_cwd(test_cwd, quiet=True):
-        main()
+from test.libregrtest import main_in_temp_cwd
 
 
 if __name__ == '__main__':
diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index cf4b84fe19..f74412720d 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -7,7 +7,8 @@ import faulthandler
 import getopt
 import os.path
 import unittest
-from test import regrtest, support, libregrtest
+from test import libregrtest
+from test import support
 
 class ParseArgsTestCase(unittest.TestCase):
 
@@ -15,7 +16,7 @@ class ParseArgsTestCase(unittest.TestCase):
 
     def checkError(self, args, msg):
         with support.captured_stderr() as err, self.assertRaises(SystemExit):
-            regrtest._parse_args(args)
+            libregrtest._parse_args(args)
         self.assertIn(msg, err.getvalue())
 
     def test_help(self):
@@ -23,82 +24,82 @@ class ParseArgsTestCase(unittest.TestCase):
             with self.subTest(opt=opt):
                 with support.captured_stdout() as out, \
                      self.assertRaises(SystemExit):
-                    regrtest._parse_args([opt])
+                    libregrtest._parse_args([opt])
                 self.assertIn('Run Python regression tests.', out.getvalue())
 
     @unittest.skipUnless(hasattr(faulthandler, 'dump_traceback_later'),
                          "faulthandler.dump_traceback_later() required")
     def test_timeout(self):
-        ns = regrtest._parse_args(['--timeout', '4.2'])
+        ns = libregrtest._parse_args(['--timeout', '4.2'])
         self.assertEqual(ns.timeout, 4.2)
         self.checkError(['--timeout'], 'expected one argument')
         self.checkError(['--timeout', 'foo'], 'invalid float value')
 
     def test_wait(self):
-        ns = regrtest._parse_args(['--wait'])
+        ns = libregrtest._parse_args(['--wait'])
         self.assertTrue(ns.wait)
 
     def test_slaveargs(self):
-        ns = regrtest._parse_args(['--slaveargs', '[[], {}]'])
+        ns = libregrtest._parse_args(['--slaveargs', '[[], {}]'])
         self.assertEqual(ns.slaveargs, '[[], {}]')
         self.checkError(['--slaveargs'], 'expected one argument')
 
     def test_start(self):
         for opt in '-S', '--start':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, 'foo'])
+                ns = libregrtest._parse_args([opt, 'foo'])
                 self.assertEqual(ns.start, 'foo')
                 self.checkError([opt], 'expected one argument')
 
     def test_verbose(self):
-        ns = regrtest._parse_args(['-v'])
+        ns = libregrtest._parse_args(['-v'])
         self.assertEqual(ns.verbose, 1)
-        ns = regrtest._parse_args(['-vvv'])
+        ns = libregrtest._parse_args(['-vvv'])
         self.assertEqual(ns.verbose, 3)
-        ns = regrtest._parse_args(['--verbose'])
+        ns = libregrtest._parse_args(['--verbose'])
         self.assertEqual(ns.verbose, 1)
-        ns = regrtest._parse_args(['--verbose'] * 3)
+        ns = libregrtest._parse_args(['--verbose'] * 3)
         self.assertEqual(ns.verbose, 3)
-        ns = regrtest._parse_args([])
+        ns = libregrtest._parse_args([])
         self.assertEqual(ns.verbose, 0)
 
     def test_verbose2(self):
         for opt in '-w', '--verbose2':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.verbose2)
 
     def test_verbose3(self):
         for opt in '-W', '--verbose3':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.verbose3)
 
     def test_quiet(self):
         for opt in '-q', '--quiet':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.quiet)
                 self.assertEqual(ns.verbose, 0)
 
     def test_slow(self):
         for opt in '-o', '--slow':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.print_slow)
 
     def test_header(self):
-        ns = regrtest._parse_args(['--header'])
+        ns = libregrtest._parse_args(['--header'])
         self.assertTrue(ns.header)
 
     def test_randomize(self):
         for opt in '-r', '--randomize':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.randomize)
 
     def test_randseed(self):
-        ns = regrtest._parse_args(['--randseed', '12345'])
+        ns = libregrtest._parse_args(['--randseed', '12345'])
         self.assertEqual(ns.random_seed, 12345)
         self.assertTrue(ns.randomize)
         self.checkError(['--randseed'], 'expected one argument')
@@ -107,7 +108,7 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_fromfile(self):
         for opt in '-f', '--fromfile':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, 'foo'])
+                ns = libregrtest._parse_args([opt, 'foo'])
                 self.assertEqual(ns.fromfile, 'foo')
                 self.checkError([opt], 'expected one argument')
                 self.checkError([opt, 'foo', '-s'], "don't go together")
@@ -115,42 +116,42 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_exclude(self):
         for opt in '-x', '--exclude':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.exclude)
 
     def test_single(self):
         for opt in '-s', '--single':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.single)
                 self.checkError([opt, '-f', 'foo'], "don't go together")
 
     def test_match(self):
         for opt in '-m', '--match':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, 'pattern'])
+                ns = libregrtest._parse_args([opt, 'pattern'])
                 self.assertEqual(ns.match_tests, 'pattern')
                 self.checkError([opt], 'expected one argument')
 
     def test_failfast(self):
         for opt in '-G', '--failfast':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, '-v'])
+                ns = libregrtest._parse_args([opt, '-v'])
                 self.assertTrue(ns.failfast)
-                ns = regrtest._parse_args([opt, '-W'])
+                ns = libregrtest._parse_args([opt, '-W'])
                 self.assertTrue(ns.failfast)
                 self.checkError([opt], '-G/--failfast needs either -v or -W')
 
     def test_use(self):
         for opt in '-u', '--use':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, 'gui,network'])
+                ns = libregrtest._parse_args([opt, 'gui,network'])
                 self.assertEqual(ns.use_resources, ['gui', 'network'])
-                ns = regrtest._parse_args([opt, 'gui,none,network'])
+                ns = libregrtest._parse_args([opt, 'gui,none,network'])
                 self.assertEqual(ns.use_resources, ['network'])
                 expected = list(libregrtest.RESOURCE_NAMES)
                 expected.remove('gui')
-                ns = regrtest._parse_args([opt, 'all,-gui'])
+                ns = libregrtest._parse_args([opt, 'all,-gui'])
                 self.assertEqual(ns.use_resources, expected)
                 self.checkError([opt], 'expected one argument')
                 self.checkError([opt, 'foo'], 'invalid resource')
@@ -158,31 +159,31 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_memlimit(self):
         for opt in '-M', '--memlimit':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, '4G'])
+                ns = libregrtest._parse_args([opt, '4G'])
                 self.assertEqual(ns.memlimit, '4G')
                 self.checkError([opt], 'expected one argument')
 
     def test_testdir(self):
-        ns = regrtest._parse_args(['--testdir', 'foo'])
+        ns = libregrtest._parse_args(['--testdir', 'foo'])
         self.assertEqual(ns.testdir, os.path.join(support.SAVEDCWD, 'foo'))
         self.checkError(['--testdir'], 'expected one argument')
 
     def test_runleaks(self):
         for opt in '-L', '--runleaks':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.runleaks)
 
     def test_huntrleaks(self):
         for opt in '-R', '--huntrleaks':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, ':'])
+                ns = libregrtest._parse_args([opt, ':'])
                 self.assertEqual(ns.huntrleaks, (5, 4, 'reflog.txt'))
-                ns = regrtest._parse_args([opt, '6:'])
+                ns = libregrtest._parse_args([opt, '6:'])
                 self.assertEqual(ns.huntrleaks, (6, 4, 'reflog.txt'))
-                ns = regrtest._parse_args([opt, ':3'])
+                ns = libregrtest._parse_args([opt, ':3'])
                 self.assertEqual(ns.huntrleaks, (5, 3, 'reflog.txt'))
-                ns = regrtest._parse_args([opt, '6:3:leaks.log'])
+                ns = libregrtest._parse_args([opt, '6:3:leaks.log'])
                 self.assertEqual(ns.huntrleaks, (6, 3, 'leaks.log'))
                 self.checkError([opt], 'expected one argument')
                 self.checkError([opt, '6'],
@@ -193,7 +194,7 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_multiprocess(self):
         for opt in '-j', '--multiprocess':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, '2'])
+                ns = libregrtest._parse_args([opt, '2'])
                 self.assertEqual(ns.use_mp, 2)
                 self.checkError([opt], 'expected one argument')
                 self.checkError([opt, 'foo'], 'invalid int value')
@@ -204,13 +205,13 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_coverage(self):
         for opt in '-T', '--coverage':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.trace)
 
     def test_coverdir(self):
         for opt in '-D', '--coverdir':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, 'foo'])
+                ns = libregrtest._parse_args([opt, 'foo'])
                 self.assertEqual(ns.coverdir,
                                  os.path.join(support.SAVEDCWD, 'foo'))
                 self.checkError([opt], 'expected one argument')
@@ -218,13 +219,13 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_nocoverdir(self):
         for opt in '-N', '--nocoverdir':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertIsNone(ns.coverdir)
 
     def test_threshold(self):
         for opt in '-t', '--threshold':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt, '1000'])
+                ns = libregrtest._parse_args([opt, '1000'])
                 self.assertEqual(ns.threshold, 1000)
                 self.checkError([opt], 'expected one argument')
                 self.checkError([opt, 'foo'], 'invalid int value')
@@ -232,13 +233,13 @@ class ParseArgsTestCase(unittest.TestCase):
     def test_nowindows(self):
         for opt in '-n', '--nowindows':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.nowindows)
 
     def test_forever(self):
         for opt in '-F', '--forever':
             with self.subTest(opt=opt):
-                ns = regrtest._parse_args([opt])
+                ns = libregrtest._parse_args([opt])
                 self.assertTrue(ns.forever)
 
 
@@ -246,26 +247,26 @@ class ParseArgsTestCase(unittest.TestCase):
         self.checkError(['--xxx'], 'usage:')
 
     def test_long_option__partial(self):
-        ns = regrtest._parse_args(['--qui'])
+        ns = libregrtest._parse_args(['--qui'])
         self.assertTrue(ns.quiet)
         self.assertEqual(ns.verbose, 0)
 
     def test_two_options(self):
-        ns = regrtest._parse_args(['--quiet', '--exclude'])
+        ns = libregrtest._parse_args(['--quiet', '--exclude'])
         self.assertTrue(ns.quiet)
         self.assertEqual(ns.verbose, 0)
         self.assertTrue(ns.exclude)
 
     def test_option_with_empty_string_value(self):
-        ns = regrtest._parse_args(['--start', ''])
+        ns = libregrtest._parse_args(['--start', ''])
         self.assertEqual(ns.start, '')
 
     def test_arg(self):
-        ns = regrtest._parse_args(['foo'])
+        ns = libregrtest._parse_args(['foo'])
         self.assertEqual(ns.args, ['foo'])
 
     def test_option_and_arg(self):
-        ns = regrtest._parse_args(['--quiet', 'foo'])
+        ns = libregrtest._parse_args(['--quiet', 'foo'])
         self.assertTrue(ns.quiet)
         self.assertEqual(ns.verbose, 0)
         self.assertEqual(ns.args, ['foo'])