cpython/Lib/test/test_support.py

import contextlib
import errno
import importlib
import io
import logging
import os
import shutil
import socket
import stat
import subprocess
import sys
import sysconfig
import tempfile
import textwrap
import unittest
import warnings

from test import support
from test.support import isolation
from test.support import import_helper
from test.support import os_helper
from test.support import script_helper
from test.support import socket_helper
from test.support import warnings_helper
from test.support.testcase import ExtraAssertions

TESTFN = os_helper.TESTFN


class LogCaptureHandler(logging.StreamHandler):
    # Inspired by pytest's caplog
    def __init__(self):
        super().__init__(io.StringIO())
        self.records = []

    def emit(self, record) -> None:
        self.records.append(record)
        super().emit(record)

    def handleError(self, record):
        raise


@contextlib.contextmanager
def _caplog():
    handler = LogCaptureHandler()
    root_logger = logging.getLogger()
    root_logger.addHandler(handler)
    try:
        yield handler
    finally:
        root_logger.removeHandler(handler)


class TestSupport(unittest.TestCase, ExtraAssertions):
    @classmethod
    def setUpClass(cls):
        orig_filter_len = len(warnings.filters)
        cls._warnings_helper_token = support.ignore_deprecations_from(
            "test.support.warnings_helper", like=".*used in test_support.*"
        )
        cls._test_support_token = support.ignore_deprecations_from(
            __name__, like=".*You should NOT be seeing this.*"
        )
        assert len(warnings.filters) == orig_filter_len + 2

    @classmethod
    def tearDownClass(cls):
        orig_filter_len = len(warnings.filters)
        support.clear_ignored_deprecations(
            cls._warnings_helper_token,
            cls._test_support_token,
        )
        assert len(warnings.filters) == orig_filter_len - 2

    def test_ignored_deprecations_are_silent(self):
        """Test support.ignore_deprecations_from() silences warnings"""
        with warnings.catch_warnings(record=True) as warning_objs:
            warnings_helper._warn_about_deprecation()
            warnings.warn("You should NOT be seeing this.", DeprecationWarning)
            messages = [str(w.message) for w in warning_objs]
        self.assertEqual(len(messages), 0, messages)

    def test_import_module(self):
        import_helper.import_module("ftplib")
        self.assertRaises(unittest.SkipTest,
                          import_helper.import_module, "foo")

    def test_import_fresh_module(self):
        import_helper.import_fresh_module("ftplib")

    def test_get_attribute(self):
        self.assertEqual(support.get_attribute(self, "test_get_attribute"),
                        self.test_get_attribute)
        self.assertRaises(unittest.SkipTest, support.get_attribute, self, "foo")

    @unittest.skip("failing buildbots")
    def test_get_original_stdout(self):
        self.assertEqual(support.get_original_stdout(), sys.stdout)

    def test_unload(self):
        import sched
        self.assertIn("sched", sys.modules)
        import_helper.unload("sched")
        self.assertNotIn("sched", sys.modules)

    def test_unlink(self):
        with open(TESTFN, "w", encoding="utf-8") as f:
            pass
        os_helper.unlink(TESTFN)
        self.assertFalse(os.path.exists(TESTFN))
        os_helper.unlink(TESTFN)

    def test_rmtree(self):
        dirpath = os_helper.TESTFN + 'd'
        subdirpath = os.path.join(dirpath, 'subdir')
        os.mkdir(dirpath)
        os.mkdir(subdirpath)
        os_helper.rmtree(dirpath)
        self.assertFalse(os.path.exists(dirpath))
        with support.swap_attr(support, 'verbose', 0):
            os_helper.rmtree(dirpath)

        os.mkdir(dirpath)
        os.mkdir(subdirpath)
        os.chmod(dirpath, stat.S_IRUSR|stat.S_IXUSR)
        with support.swap_attr(support, 'verbose', 0):
            os_helper.rmtree(dirpath)
        self.assertFalse(os.path.exists(dirpath))

        os.mkdir(dirpath)
        os.mkdir(subdirpath)
        os.chmod(dirpath, 0)
        with support.swap_attr(support, 'verbose', 0):
            os_helper.rmtree(dirpath)
        self.assertFalse(os.path.exists(dirpath))

    def test_forget(self):
        mod_filename = TESTFN + '.py'
        with open(mod_filename, 'w', encoding="utf-8") as f:
            print('foo = 1', file=f)
        sys.path.insert(0, os.curdir)
        importlib.invalidate_caches()
        try:
            mod = __import__(TESTFN)
            self.assertIn(TESTFN, sys.modules)

            import_helper.forget(TESTFN)
            self.assertNotIn(TESTFN, sys.modules)
        finally:
            del sys.path[0]
            os_helper.unlink(mod_filename)
            os_helper.rmtree('__pycache__')

    @support.requires_working_socket()
    def test_HOST(self):
        s = socket.create_server((socket_helper.HOST, 0))
        s.close()

    @support.requires_working_socket()
    def test_find_unused_port(self):
        port = socket_helper.find_unused_port()
        s = socket.create_server((socket_helper.HOST, port))
        s.close()

    @support.requires_working_socket()
    def test_bind_port(self):
        s = socket.socket()
        socket_helper.bind_port(s)
        s.listen()
        s.close()

    # Tests for temp_dir()

    def test_temp_dir(self):
        """Test that temp_dir() creates and destroys its directory."""
        parent_dir = tempfile.mkdtemp()
        parent_dir = os.path.realpath(parent_dir)

        try:
            path = os.path.join(parent_dir, 'temp')
            self.assertFalse(os.path.isdir(path))
            with os_helper.temp_dir(path) as temp_path:
                self.assertEqual(temp_path, path)
                self.assertTrue(os.path.isdir(path))
            self.assertFalse(os.path.isdir(path))
        finally:
            os_helper.rmtree(parent_dir)

    def test_temp_dir__path_none(self):
        """Test passing no path."""
        with os_helper.temp_dir() as temp_path:
            self.assertTrue(os.path.isdir(temp_path))
        self.assertFalse(os.path.isdir(temp_path))

    def test_temp_dir__existing_dir__quiet_default(self):
        """Test passing a directory that already exists."""
        def call_temp_dir(path):
            with os_helper.temp_dir(path) as temp_path:
                raise Exception("should not get here")

        path = tempfile.mkdtemp()
        path = os.path.realpath(path)
        try:
            self.assertTrue(os.path.isdir(path))
            self.assertRaises(FileExistsError, call_temp_dir, path)
            # Make sure temp_dir did not delete the original directory.
            self.assertTrue(os.path.isdir(path))
        finally:
            shutil.rmtree(path)

    def test_temp_dir__existing_dir__quiet_true(self):
        """Test passing a directory that already exists with quiet=True."""
        path = tempfile.mkdtemp()
        path = os.path.realpath(path)

        try:
            with warnings_helper.check_warnings() as recorder, _caplog() as caplog:
                with os_helper.temp_dir(path, quiet=True) as temp_path:
                    self.assertEqual(path, temp_path)
                warnings = [str(w.message) for w in recorder.warnings]
            # Make sure temp_dir did not delete the original directory.
            self.assertTrue(os.path.isdir(path))
        finally:
            shutil.rmtree(path)

        self.assertListEqual(warnings, [])
        self.assertEqual(len(caplog.records), 1)
        record = caplog.records[0]
        self.assertStartsWith(
            record.getMessage(),
            f'tests may fail, unable to create '
            f'temporary directory {path!r}: '
        )

    @support.requires_fork()
    def test_temp_dir__forked_child(self):
        """Test that a forked child process does not remove the directory."""
        # See bpo-30028 for details.
        # Run the test as an external script, because it uses fork.
        script_helper.assert_python_ok("-c", textwrap.dedent("""
            import os
            from test import support
            from test.support import os_helper
            with os_helper.temp_cwd() as temp_path:
                pid = os.fork()
                if pid != 0:
                    # parent process

                    # wait for the child to terminate
                    support.wait_process(pid, exitcode=0)

                    # Make sure that temp_path is still present. When the child
                    # process leaves the 'temp_cwd'-context, the __exit__()-
                    # method of the context must not remove the temporary
                    # directory.
                    if not os.path.isdir(temp_path):
                        raise AssertionError("Child removed temp_path.")
        """))

    # Tests for change_cwd()

    def test_change_cwd(self):
        original_cwd = os.getcwd()

        with os_helper.temp_dir() as temp_path:
            with os_helper.change_cwd(temp_path) as new_cwd:
                self.assertEqual(new_cwd, temp_path)
                self.assertEqual(os.getcwd(), new_cwd)

        self.assertEqual(os.getcwd(), original_cwd)

    def test_change_cwd__non_existent_dir(self):
        """Test passing a non-existent directory."""
        original_cwd = os.getcwd()

        def call_change_cwd(path):
            with os_helper.change_cwd(path) as new_cwd:
                raise Exception("should not get here")

        with os_helper.temp_dir() as parent_dir:
            non_existent_dir = os.path.join(parent_dir, 'does_not_exist')
            self.assertRaises(FileNotFoundError, call_change_cwd,
                              non_existent_dir)

        self.assertEqual(os.getcwd(), original_cwd)

    def test_change_cwd__non_existent_dir__quiet_true(self):
        """Test passing a non-existent directory with quiet=True."""
        original_cwd = os.getcwd()

        with os_helper.temp_dir() as parent_dir:
            bad_dir = os.path.join(parent_dir, 'does_not_exist')
            with warnings_helper.check_warnings() as recorder, _caplog() as caplog:
                with os_helper.change_cwd(bad_dir, quiet=True) as new_cwd:
                    self.assertEqual(new_cwd, original_cwd)
                    self.assertEqual(os.getcwd(), new_cwd)
                warnings = [str(w.message) for w in recorder.warnings]

        self.assertListEqual(warnings, [])
        self.assertEqual(len(caplog.records), 1)
        record = caplog.records[0]
        self.assertStartsWith(
            record.getMessage(),
            f'tests may fail, unable to change '
            f'the current working directory '
            f'to {bad_dir!r}: '
        )

    # Tests for change_cwd()

    def test_change_cwd__chdir_warning(self):
        """Check the warning message when os.chdir() fails."""
        path = TESTFN + '_does_not_exist'
        with warnings_helper.check_warnings() as recorder, _caplog() as caplog:
            with os_helper.change_cwd(path=path, quiet=True):
                pass
            messages = [str(w.message) for w in recorder.warnings]

        self.assertListEqual(messages, [])
        self.assertEqual(len(caplog.records), 1)
        record = caplog.records[0]
        self.assertStartsWith(
            record.getMessage(),
            f'tests may fail, unable to change '
            f'the current working directory '
            f'to {path!r}: ',
        )

    # Tests for temp_cwd()

    def test_temp_cwd(self):
        here = os.getcwd()
        with os_helper.temp_cwd(name=TESTFN):
            self.assertEqual(os.path.basename(os.getcwd()), TESTFN)
        self.assertFalse(os.path.exists(TESTFN))
        self.assertEqual(os.getcwd(), here)


    def test_temp_cwd__name_none(self):
        """Test passing None to temp_cwd()."""
        original_cwd = os.getcwd()
        with os_helper.temp_cwd(name=None) as new_cwd:
            self.assertNotEqual(new_cwd, original_cwd)
            self.assertTrue(os.path.isdir(new_cwd))
            self.assertEqual(os.getcwd(), new_cwd)
        self.assertEqual(os.getcwd(), original_cwd)

    def test_sortdict(self):
        self.assertEqual(support.sortdict({3:3, 2:2, 1:1}), "{1: 1, 2: 2, 3: 3}")

    def test_make_bad_fd(self):
        fd = os_helper.make_bad_fd()
        with self.assertRaises(OSError) as cm:
            os.write(fd, b"foo")
        self.assertEqual(cm.exception.errno, errno.EBADF)

    def test_check_syntax_error(self):
        support.check_syntax_error(self, "def class", lineno=1, offset=5)
        with self.assertRaises(AssertionError):
            support.check_syntax_error(self, "x=1")

    def test_CleanImport(self):
        import importlib
        with import_helper.CleanImport("pprint"):
            importlib.import_module("pprint")

    def test_DirsOnSysPath(self):
        with import_helper.DirsOnSysPath('foo', 'bar'):
            self.assertIn("foo", sys.path)
            self.assertIn("bar", sys.path)
        self.assertNotIn("foo", sys.path)
        self.assertNotIn("bar", sys.path)

    def test_captured_stdout(self):
        with support.captured_stdout() as stdout:
            print("hello")
        self.assertEqual(stdout.getvalue(), "hello\n")

    def test_captured_stderr(self):
        with support.captured_stderr() as stderr:
            print("hello", file=sys.stderr)
        self.assertEqual(stderr.getvalue(), "hello\n")

    def test_captured_stdin(self):
        with support.captured_stdin() as stdin:
            stdin.write('hello\n')
            stdin.seek(0)
            # call test code that consumes from sys.stdin
            captured = input()
        self.assertEqual(captured, "hello")

    def test_gc_collect(self):
        support.gc_collect()

    def test_python_is_optimized(self):
        self.assertIsInstance(support.python_is_optimized(), bool)

    def test_swap_attr(self):
        class Obj:
            pass
        obj = Obj()
        obj.x = 1
        with support.swap_attr(obj, "x", 5) as x:
            self.assertEqual(obj.x, 5)
            self.assertEqual(x, 1)
        self.assertEqual(obj.x, 1)
        with support.swap_attr(obj, "y", 5) as y:
            self.assertEqual(obj.y, 5)
            self.assertIsNone(y)
        self.assertFalse(hasattr(obj, 'y'))
        with support.swap_attr(obj, "y", 5):
            del obj.y
        self.assertFalse(hasattr(obj, 'y'))

    def test_swap_item(self):
        D = {"x":1}
        with support.swap_item(D, "x", 5) as x:
            self.assertEqual(D["x"], 5)
            self.assertEqual(x, 1)
        self.assertEqual(D["x"], 1)
        with support.swap_item(D, "y", 5) as y:
            self.assertEqual(D["y"], 5)
            self.assertIsNone(y)
        self.assertNotIn("y", D)
        with support.swap_item(D, "y", 5):
            del D["y"]
        self.assertNotIn("y", D)

    class RefClass:
        attribute1 = None
        attribute2 = None
        _hidden_attribute1 = None
        __magic_1__ = None

    class OtherClass:
        attribute2 = None
        attribute3 = None
        __magic_1__ = None
        __magic_2__ = None

    def test_detect_api_mismatch(self):
        missing_items = support.detect_api_mismatch(self.RefClass,
                                                    self.OtherClass)
        self.assertEqual({'attribute1'}, missing_items)

        missing_items = support.detect_api_mismatch(self.OtherClass,
                                                    self.RefClass)
        self.assertEqual({'attribute3', '__magic_2__'}, missing_items)

    def test_detect_api_mismatch__ignore(self):
        ignore = ['attribute1', 'attribute3', '__magic_2__', 'not_in_either']

        missing_items = support.detect_api_mismatch(
                self.RefClass, self.OtherClass, ignore=ignore)
        self.assertEqual(set(), missing_items)

        missing_items = support.detect_api_mismatch(
                self.OtherClass, self.RefClass, ignore=ignore)
        self.assertEqual(set(), missing_items)

    def test_check__all__(self):
        extra = {'tempdir'}
        not_exported = {'template'}
        support.check__all__(self,
                             tempfile,
                             extra=extra,
                             not_exported=not_exported)

        extra = {
            'TextTestResult',
            'installHandler',
        }
        not_exported = {'load_tests', "TestProgram", "BaseTestSuite"}
        support.check__all__(self,
                             unittest,
                             ("unittest.result", "unittest.case",
                              "unittest.suite", "unittest.loader",
                              "unittest.main", "unittest.runner",
                              "unittest.signals", "unittest.async_case"),
                             extra=extra,
                             not_exported=not_exported)

        self.assertRaises(AssertionError, support.check__all__, self, unittest)

    @unittest.skipUnless(hasattr(os, 'waitpid') and hasattr(os, 'WNOHANG'),
                         'need os.waitpid() and os.WNOHANG')
    @support.requires_fork()
    def test_reap_children(self):
        # Make sure that there is no other pending child process
        support.reap_children()

        # Create a child process
        pid = os.fork()
        if pid == 0:
            # child process: do nothing, just exit
            os._exit(0)

        was_altered = support.environment_altered
        try:
            support.environment_altered = False
            stderr = io.StringIO()

            for _ in support.sleeping_retry(support.SHORT_TIMEOUT):
                with support.swap_attr(support.print_warning, 'orig_stderr', stderr):
                    support.reap_children()

                # Use environment_altered to check if reap_children() found
                # the child process
                if support.environment_altered:
                    break

            msg = "Warning -- reap_children() reaped child process %s" % pid
            self.assertIn(msg, stderr.getvalue())
            self.assertTrue(support.environment_altered)
        finally:
            support.environment_altered = was_altered

        # Just in case, check again that there is no other
        # pending child process
        support.reap_children()

    @support.requires_subprocess()
    def check_options(self, args, func, expected=None):
        code = f'from test.support import {func}; print(repr({func}()))'
        cmd = [sys.executable, *args, '-c', code]
        env = {key: value for key, value in os.environ.items()
               if not key.startswith('PYTHON')}
        proc = subprocess.run(cmd,
                              stdout=subprocess.PIPE,
                              stderr=subprocess.DEVNULL,
                              universal_newlines=True,
                              env=env)
        if expected is None:
            expected = args
        self.assertEqual(proc.stdout.rstrip(), repr(expected))
        self.assertEqual(proc.returncode, 0)

    @support.requires_resource('cpu')
    def test_args_from_interpreter_flags(self):
        # Test test.support.args_from_interpreter_flags()
        for opts in (
            # no option
            [],
            # single option
            ['-B'],
            ['-s'],
            ['-S'],
            ['-E'],
            ['-v'],
            ['-b'],
            ['-P'],
            ['-q'],
            ['-I'],
            # same option multiple times
            ['-bb'],
            ['-vvv'],
            # -W options
            ['-Wignore'],
            # -X options
            ['-X', 'dev'],
            ['-Wignore', '-X', 'dev'],
            ['-X', 'cpu_count=4'],
            ['-X', 'disable-remote-debug'],
            ['-X', 'faulthandler'],
            ['-X', 'importtime'],
            ['-X', 'importtime=2'],
            ['-X', 'int_max_str_digits=1000'],
            ['-X', 'lazy_imports=all'],
            ['-X', 'no_debug_ranges'],
            ['-X', 'showrefcount'],
            ['-X', 'tracemalloc'],
            ['-X', 'tracemalloc=3'],
            ['-X', 'warn_default_encoding'],
        ):
            with self.subTest(opts=opts):
                self.check_options(opts, 'args_from_interpreter_flags')

        with os_helper.temp_dir() as temp_path:
            prefix = os.path.join(temp_path, 'pycache')
            opts = ['-X', f'pycache_prefix={prefix}']
            with self.subTest(opts=opts):
                self.check_options(opts, 'args_from_interpreter_flags')

        self.check_options(['-I', '-E', '-s', '-P'],
                           'args_from_interpreter_flags',
                           ['-I'])

    def test_optim_args_from_interpreter_flags(self):
        # Test test.support.optim_args_from_interpreter_flags()
        for opts in (
            # no option
            [],
            ['-O'],
            ['-OO'],
            ['-OOOO'],
        ):
            with self.subTest(opts=opts):
                self.check_options(opts, 'optim_args_from_interpreter_flags')

    @unittest.skipIf(support.is_apple_mobile, "Unstable on Apple Mobile")
    @unittest.skipIf(support.is_emscripten, "Unstable in Emscripten")
    @unittest.skipIf(support.is_wasi, "Unavailable on WASI")
    def test_fd_count(self):
        # We cannot test the absolute value of fd_count(): on old Linux kernel
        # or glibc versions, os.urandom() keeps a FD open on /dev/urandom
        # device and Python has 4 FD opens instead of 3. Test is unstable on
        # Emscripten and Apple Mobile platforms; these platforms start and stop
        # background threads that use pipes and epoll fds.
        start = os_helper.fd_count()
        fd = os.open(__file__, os.O_RDONLY)
        try:
            more = os_helper.fd_count()
        finally:
            os.close(fd)
        self.assertEqual(more - start, 1)

    def check_print_warning(self, msg, expected):
        stderr = io.StringIO()
        with support.swap_attr(support.print_warning, 'orig_stderr', stderr):
            support.print_warning(msg)
        self.assertEqual(stderr.getvalue(), expected)

    def test_print_warning(self):
        self.check_print_warning("msg",
                                 "Warning -- msg\n")
        self.check_print_warning("a\nb",
                                 'Warning -- a\nWarning -- b\n')

    def test_has_strftime_extensions(self):
        if support.is_emscripten or sys.platform == "win32":
            self.assertFalse(support.has_strftime_extensions)
        else:
            self.assertTrue(support.has_strftime_extensions)

    def test_get_recursion_depth(self):
        # test support.get_recursion_depth()
        code = textwrap.dedent("""
            from test import support
            import sys

            def check(cond):
                if not cond:
                    raise AssertionError("test failed")

            # depth 1
            check(support.get_recursion_depth() == 1)

            # depth 2
            def test_func():
                check(support.get_recursion_depth() == 2)
            test_func()

            def test_recursive(depth, limit):
                if depth >= limit:
                    # cannot call get_recursion_depth() at this depth,
                    # it can raise RecursionError
                    return
                get_depth = support.get_recursion_depth()
                print(f"test_recursive: {depth}/{limit}: "
                      f"get_recursion_depth() says {get_depth}")
                check(get_depth == depth)
                test_recursive(depth + 1, limit)

            # depth up to 25
            with support.infinite_recursion(max_depth=25):
                limit = sys.getrecursionlimit()
                print(f"test with sys.getrecursionlimit()={limit}")
                test_recursive(2, limit)

            # depth up to 500
            with support.infinite_recursion(max_depth=500):
                limit = sys.getrecursionlimit()
                print(f"test with sys.getrecursionlimit()={limit}")
                test_recursive(2, limit)
        """)
        script_helper.assert_python_ok("-c", code)

    def test_recursion(self):
        # Test infinite_recursion() and get_recursion_available() functions.
        def recursive_function(depth):
            if depth:
                recursive_function(depth - 1)

        for max_depth in (5, 25, 250, 2500):
            with support.infinite_recursion(max_depth):
                available = support.get_recursion_available()

                # Recursion up to 'available' additional frames should be OK.
                recursive_function(available)

                # Recursion up to 'available+1' additional frames must raise
                # RecursionError. Avoid self.assertRaises(RecursionError) which
                # can consume more than 3 frames and so raises RecursionError.
                try:
                    recursive_function(available + 1)
                except RecursionError:
                    pass
                else:
                    self.fail("RecursionError was not raised")

        # Test the bare minimumum: max_depth=3
        with support.infinite_recursion(3):
            try:
                recursive_function(3)
            except RecursionError:
                pass
            else:
                self.fail("RecursionError was not raised")

    def test_parse_memlimit(self):
        parse = support._parse_memlimit
        KiB = 1024
        MiB = KiB * 1024
        GiB = MiB * 1024
        TiB = GiB * 1024
        self.assertEqual(parse('0k'), 0)
        self.assertEqual(parse('3k'), 3 * KiB)
        self.assertEqual(parse('2.4m'), int(2.4 * MiB))
        self.assertEqual(parse('4g'), int(4 * GiB))
        self.assertEqual(parse('1t'), TiB)

        for limit in ('', '3', '3.5.10k', '10x'):
            with self.subTest(limit=limit):
                with self.assertRaises(ValueError):
                    parse(limit)

    def test_set_memlimit(self):
        _4GiB = 4 * 1024 ** 3
        TiB = 1024 ** 4
        old_max_memuse = support.max_memuse
        old_real_max_memuse = support.real_max_memuse
        try:
            if sys.maxsize > 2**32:
                support.set_memlimit('4g')
                self.assertEqual(support.max_memuse, _4GiB)
                self.assertEqual(support.real_max_memuse, _4GiB)

                big = 2**100 // TiB
                support.set_memlimit(f'{big}t')
                self.assertEqual(support.max_memuse, sys.maxsize)
                self.assertEqual(support.real_max_memuse, big * TiB)
            else:
                support.set_memlimit('4g')
                self.assertEqual(support.max_memuse, sys.maxsize)
                self.assertEqual(support.real_max_memuse, _4GiB)
        finally:
            support.max_memuse = old_max_memuse
            support.real_max_memuse = old_real_max_memuse

    def test_copy_python_src_ignore(self):
        # Get source directory
        src_dir = sysconfig.get_config_var('abs_srcdir')
        if not src_dir:
            src_dir = sysconfig.get_config_var('srcdir')
        src_dir = os.path.abspath(src_dir)

        # Check that the source code is available
        if not os.path.exists(src_dir):
            self.skipTest(f"cannot access Python source code directory:"
                          f" {src_dir!r}")
        # Check that the landmark copy_python_src_ignore() expects is available
        # (Previously we looked for 'Lib\os.py', which is always present on Windows.)
        landmark = os.path.join(src_dir, 'Modules')
        if not os.path.exists(landmark):
            self.skipTest(f"cannot access Python source code directory:"
                          f" {landmark!r} landmark is missing")

        # Test support.copy_python_src_ignore()

        # Source code directory
        ignored = {'.git', '__pycache__'}
        names = os.listdir(src_dir)
        self.assertEqual(support.copy_python_src_ignore(src_dir, names),
                         ignored | {'build'})

        # Doc/ directory
        path = os.path.join(src_dir, 'Doc')
        self.assertEqual(support.copy_python_src_ignore(path, os.listdir(path)),
                         ignored | {'build', 'venv'})

        # Another directory
        path = os.path.join(src_dir, 'Objects')
        self.assertEqual(support.copy_python_src_ignore(path, os.listdir(path)),
                         ignored)

    def test_linked_to_musl(self):
        linked = support.linked_to_musl()
        self.assertIsInstance(linked, bool)

    # XXX -follows a list of untested API
    # make_legacy_pyc
    # is_resource_enabled
    # requires
    # fcmp
    # umaks
    # findfile
    # check_warnings
    # EnvironmentVarGuard
    # transient_internet
    # run_with_locale
    # bigmemtest
    # precisionbigmemtest
    # bigaddrspacetest
    # requires_resource
    # threading_cleanup
    # reap_threads
    # can_symlink
    # skip_unless_symlink
    # SuppressCrashReport


class TestIsolated(unittest.TestCase):
    # Drive the sample tests in test._isolated_sample (which really spawn
    # subprocesses through @isolation.runInSubprocess()) under a private
    # TestResult, and check that each subprocess outcome is replayed in the parent.

    @staticmethod
    def _run(name):
        suite = unittest.TestLoader().loadTestsFromName(
            'test._isolated_sample.' + name)
        result = unittest.TestResult()
        suite.run(result)
        return result

    @staticmethod
    def _names(items):
        # Map outcome entries (which are (test, detail) pairs, except
        # unexpectedSuccesses which are bare tests) to their method names.
        names = []
        for item in items:
            test = item[0] if isinstance(item, tuple) else item
            names.append(test.id().rpartition('.')[2])
        return sorted(names)

    @support.requires_subprocess()
    def test_method_outcomes(self):
        result = self._run('MethodSample')
        self.assertEqual(result.testsRun, 6)
        self.assertEqual(self._names(result.failures), ['test_fail'])
        self.assertEqual(self._names(result.errors), ['test_error'])
        self.assertEqual(self._names(result.skipped), ['test_skip'])
        self.assertEqual(self._names(result.expectedFailures),
                         ['test_expected_failure'])
        self.assertEqual(self._names(result.unexpectedSuccesses),
                         ['test_unexpected_success'])

    @support.requires_subprocess()
    def test_class_outcomes(self):
        result = self._run('ClassSample')
        self.assertEqual(result.testsRun, 3)
        self.assertEqual(self._names(result.failures), ['test_fail'])
        self.assertEqual(self._names(result.expectedFailures),
                         ['test_expected_failure'])
        self.assertEqual(result.errors, [])
        self.assertEqual(result.unexpectedSuccesses, [])

    @support.requires_subprocess()
    def test_subtests_reported_individually(self):
        result = self._run('SubtestSample')
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.failures), 1)
        test, _ = result.failures[0]
        self.assertIn('i=1', str(test))

    @support.requires_subprocess()
    def test_skip_reason_propagated(self):
        result = self._run('MethodSample.test_skip')
        self.assertEqual([reason for _, reason in result.skipped], ['nope'])

    @support.requires_subprocess()
    def test_subprocess_traceback_is_cause(self):
        result = self._run('MethodSample.test_fail')
        self.assertEqual(len(result.failures), 1)
        _, tb = result.failures[0]
        # The real assertion that failed in the subprocess is shown ...
        self.assertIn('self.assertEqual(1, 2)', tb)
        # ... as the direct cause of the replayed failure ...
        self.assertIn('direct cause', tb)
        # ... without leaking the parent-side replay frames.
        self.assertNotIn('isolation.py', tb)

    @support.requires_subprocess()
    def test_durations_forwarded_for_class(self):
        from test._isolated_sample import DURATION_SLEEP
        result = unittest.TestResult()
        suite = unittest.TestLoader().loadTestsFromName(
            'test._isolated_sample.DurationSample')
        suite.run(result)
        # The duration reported in the parent is the one measured in the
        # subprocess (around the sleep), not the near-instant replay time.
        self.assertEqual(len(result.collectedDurations), 1)
        name, elapsed = result.collectedDurations[0]
        self.assertEqual(name.split()[0], 'test_slow')
        self.assertGreaterEqual(elapsed, DURATION_SLEEP / 2)

    @support.requires_subprocess()
    def test_subclass_of_isolated_class(self):
        # Both samples pass only if the fixtures are bound to the runtime class
        # and what the subclass adds or overrides runs in the subprocess.
        for name, count in (('SubclassingSample', 1), ('SubclassSample', 2)):
            with self.subTest(sample=name):
                result = self._run(name)
                self.assertEqual(result.testsRun, count)
                self.assertEqual(result.failures, [])
                self.assertEqual(result.errors, [])

    @support.requires_subprocess()
    def test_subclass_bypassing_setupclass_is_reported(self):
        # A class that never ran in a subprocess must error out, not pass with
        # no outcome to replay.
        result = self._run('BrokenSubclassSample')
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.errors), 1)
        self.assertIn('did not run in a subprocess', result.errors[0][1])

    @support.requires_subprocess()
    def test_subprocess_dying_after_the_test_is_reported(self):
        from test._isolated_sample import EXIT_CODE
        result = self._run('MethodExitSample.test_passes_then_dies')
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.errors), 1)
        self.assertIn(f'exited with code {EXIT_CODE}', result.errors[0][1])

    @support.requires_subprocess()
    def test_subprocess_dying_does_not_hide_the_failure(self):
        result = self._run('MethodExitSample.test_fails_and_dies')
        self.assertEqual(self._names(result.failures), ['test_fails_and_dies'])
        self.assertEqual(result.errors, [])

    @support.requires_subprocess()
    def test_class_subprocess_dying_after_the_tests_is_reported(self):
        # The tests that ran are still reported, and the crash once, for the class.
        from test._isolated_sample import EXIT_CODE
        result = self._run('ClassExitSample')
        self.assertEqual(result.testsRun, 2)
        self.assertEqual(result.failures, [])
        self.assertEqual(len(result.errors), 1)
        self.assertIn('tearDownClass', str(result.errors[0][0]))
        self.assertIn(f'exited with code {EXIT_CODE}', result.errors[0][1])

    @support.requires_subprocess()
    def test_options_passed_to_subprocess(self):
        result = self._run('OptionsSample')
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(result.failures, [])
        self.assertEqual(result.errors, [])

    @support.requires_subprocess()
    def test_env_passed_to_subprocess(self):
        # The samples check the variable, so set it here to let them tell
        # env= from the inherited environment.
        with os_helper.EnvironmentVarGuard() as env:
            env['_PYTHON_ISOLATION_PROBE'] = 'set-by-parent'
            result = self._run('EnvSample')
        self.assertEqual(result.testsRun, 3)
        self.assertEqual(result.failures, [])
        self.assertEqual(result.errors, [])

    @support.requires_subprocess()
    def test_timeout_reported_as_error(self):
        from test._isolated_sample import TIMEOUT
        result = self._run('TimeoutSample')
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.errors), 1)
        self.assertIn(f'within {TIMEOUT} seconds', result.errors[0][1])

    @support.requires_subprocess()
    def test_bigmemtest_isolates_a_real_run(self):
        # A dummy run (no -M) stays in this process, a real run does not.
        for memlimit in (0, support._1G):
            with self.subTest(real_max_memuse=memlimit):
                with support.swap_attr(support, 'real_max_memuse', memlimit):
                    result = self._run('BigmemSample')
                self.assertEqual(result.testsRun, 1)
                self.assertEqual(self._names(result.failures), [])
                self.assertEqual(self._names(result.errors), [])

    def test_skipped_without_subprocess_support(self):
        # On a platform without subprocess support the test is skipped in the
        # parent, before any subprocess is spawned.
        calls = []
        orig = isolation._start_test
        with support.swap_attr(support, 'has_subprocess_support', False):
            isolation._start_test = lambda *a, **k: calls.append(a)
            try:
                result = self._run('MethodSample.test_pass')
            finally:
                isolation._start_test = orig
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.skipped), 1)
        self.assertEqual(calls, [])


class TestSubTests(ExtraAssertions, unittest.TestCase):

    def run_test(self, cls):
        result = unittest.TestResult()
        cls('test_it').run(result)
        return result

    def test_sync(self):
        ran = []

        class Sample(unittest.TestCase):
            @support.subTests('a', [1, 2, 3])
            def test_it(self, a):
                ran.append(a)
                self.assertNotEqual(a, 2)

        result = self.run_test(Sample)
        self.assertEqual(ran, [1, 2, 3])
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.failures), 1)
        self.assertEndsWith(result.failures[0][0].id(), 'test_it (a=2)')

    # Running an asyncio event loop needs a working socket.
    @support.requires_working_socket()
    def test_async(self):
        # Running an event loop sets the event loop policy, which regrtest
        # reports as a change of the environment.
        import asyncio.events
        self.enterContext(
            support.swap_attr(asyncio.events, '_event_loop_policy', None))

        # An asynchronous test must be awaited: a synchronous wrapper would
        # make it silently not run at all.
        ran = []

        class Sample(unittest.IsolatedAsyncioTestCase):
            @support.subTests('a', [1, 2, 3])
            async def test_it(self, a):
                ran.append(a)
                self.assertNotEqual(a, 2)

        result = self.run_test(Sample)
        self.assertEqual(ran, [1, 2, 3])
        self.assertEqual(result.testsRun, 1)
        self.assertEqual(len(result.failures), 1)
        self.assertEndsWith(result.failures[0][0].id(), 'test_it (a=2)')

    def test_multiple_parameters(self):
        ran = []

        class Sample(unittest.TestCase):
            @support.subTests('a,b', [(1, 'x'), (2, 'y')])
            def test_it(self, a, b):
                ran.append((a, b))

        result = self.run_test(Sample)
        self.assertTrue(result.wasSuccessful(), result.errors)
        self.assertEqual(ran, [(1, 'x'), (2, 'y')])

    def test_cannot_decorate_class(self):
        with self.assertRaises(TypeError):
            @support.subTests('a', [1])
            class Sample(unittest.TestCase):
                pass


if __name__ == '__main__':
    unittest.main()