gh-76785: Fixes for test.support.interpreters (gh-112982)

This involves a number of changes for PEP 734.

8 files changed, 1512 insertions, 0 deletions

diff --git a/Lib/test/test_interpreters/__init__.py b/Lib/test/test_interpreters/__init__.py
new file mode 100644
index 0000000..4b16ecc
--- /dev/null
+++ b/Lib/test/test_interpreters/__init__.py
@@ -0,0 +1,5 @@
+import os
+from test.support import load_package_tests
+
+def load_tests(*args):
+    return load_package_tests(os.path.dirname(__file__), *args)
diff --git a/Lib/test/test_interpreters/__main__.py b/Lib/test/test_interpreters/__main__.py
new file mode 100644
index 0000000..8641229
--- /dev/null
+++ b/Lib/test/test_interpreters/__main__.py
@@ -0,0 +1,4 @@
+from . import load_tests
+import unittest
+
+nittest.main()
diff --git a/Lib/test/test_interpreters/test_api.py b/Lib/test/test_interpreters/test_api.py
new file mode 100644
index 0000000..e4ae9d0
--- /dev/null
+++ b/Lib/test/test_interpreters/test_api.py
@@ -0,0 +1,642 @@
+import os
+import threading
+from textwrap import dedent
+import unittest
+
+from test import support
+from test.support import import_helper
+# Raise SkipTest if subinterpreters not supported.
+import_helper.import_module('_xxsubinterpreters')
+from test.support import interpreters
+from test.support.interpreters import InterpreterNotFoundError
+from .utils import _captured_script, _run_output, _running, TestBase
+
+
+class ModuleTests(TestBase):
+
+    def test_queue_aliases(self):
+        first = [
+            interpreters.create_queue,
+            interpreters.Queue,
+            interpreters.QueueEmpty,
+            interpreters.QueueFull,
+        ]
+        second = [
+            interpreters.create_queue,
+            interpreters.Queue,
+            interpreters.QueueEmpty,
+            interpreters.QueueFull,
+        ]
+        self.assertEqual(second, first)
+
+
+class CreateTests(TestBase):
+
+    def test_in_main(self):
+        interp = interpreters.create()
+        self.assertIsInstance(interp, interpreters.Interpreter)
+        self.assertIn(interp, interpreters.list_all())
+
+    def test_in_thread(self):
+        lock = threading.Lock()
+        interp = None
+        def f():
+            nonlocal interp
+            interp = interpreters.create()
+            lock.acquire()
+            lock.release()
+        t = threading.Thread(target=f)
+        with lock:
+            t.start()
+        t.join()
+        self.assertIn(interp, interpreters.list_all())
+
+    def test_in_subinterpreter(self):
+        main, = interpreters.list_all()
+        interp = interpreters.create()
+        out = _run_output(interp, dedent("""
+            from test.support import interpreters
+            interp = interpreters.create()
+            print(interp.id)
+            """))
+        interp2 = interpreters.Interpreter(int(out))
+        self.assertEqual(interpreters.list_all(), [main, interp, interp2])
+
+    def test_after_destroy_all(self):
+        before = set(interpreters.list_all())
+        # Create 3 subinterpreters.
+        interp_lst = []
+        for _ in range(3):
+            interps = interpreters.create()
+            interp_lst.append(interps)
+        # Now destroy them.
+        for interp in interp_lst:
+            interp.close()
+        # Finally, create another.
+        interp = interpreters.create()
+        self.assertEqual(set(interpreters.list_all()), before | {interp})
+
+    def test_after_destroy_some(self):
+        before = set(interpreters.list_all())
+        # Create 3 subinterpreters.
+        interp1 = interpreters.create()
+        interp2 = interpreters.create()
+        interp3 = interpreters.create()
+        # Now destroy 2 of them.
+        interp1.close()
+        interp2.close()
+        # Finally, create another.
+        interp = interpreters.create()
+        self.assertEqual(set(interpreters.list_all()), before | {interp3, interp})
+
+
+class GetMainTests(TestBase):
+
+    def test_id(self):
+        main = interpreters.get_main()
+        self.assertEqual(main.id, 0)
+
+    def test_current(self):
+        main = interpreters.get_main()
+        current = interpreters.get_current()
+        self.assertIs(main, current)
+
+    def test_idempotent(self):
+        main1 = interpreters.get_main()
+        main2 = interpreters.get_main()
+        self.assertIs(main1, main2)
+
+
+class GetCurrentTests(TestBase):
+
+    def test_main(self):
+        main = interpreters.get_main()
+        current = interpreters.get_current()
+        self.assertEqual(current, main)
+
+    def test_subinterpreter(self):
+        main = interpreters.get_main()
+        interp = interpreters.create()
+        out = _run_output(interp, dedent("""
+            from test.support import interpreters
+            cur = interpreters.get_current()
+            print(cur.id)
+            """))
+        current = interpreters.Interpreter(int(out))
+        self.assertEqual(current, interp)
+        self.assertNotEqual(current, main)
+
+    def test_idempotent(self):
+        with self.subTest('main'):
+            cur1 = interpreters.get_current()
+            cur2 = interpreters.get_current()
+            self.assertIs(cur1, cur2)
+
+        with self.subTest('subinterpreter'):
+            interp = interpreters.create()
+            out = _run_output(interp, dedent("""
+                from test.support import interpreters
+                cur = interpreters.get_current()
+                print(id(cur))
+                cur = interpreters.get_current()
+                print(id(cur))
+                """))
+            objid1, objid2 = (int(v) for v in out.splitlines())
+            self.assertEqual(objid1, objid2)
+
+        with self.subTest('per-interpreter'):
+            interp = interpreters.create()
+            out = _run_output(interp, dedent("""
+                from test.support import interpreters
+                cur = interpreters.get_current()
+                print(id(cur))
+                """))
+            id1 = int(out)
+            id2 = id(interp)
+            self.assertNotEqual(id1, id2)
+
+
+class ListAllTests(TestBase):
+
+    def test_initial(self):
+        interps = interpreters.list_all()
+        self.assertEqual(1, len(interps))
+
+    def test_after_creating(self):
+        main = interpreters.get_current()
+        first = interpreters.create()
+        second = interpreters.create()
+
+        ids = []
+        for interp in interpreters.list_all():
+            ids.append(interp.id)
+
+        self.assertEqual(ids, [main.id, first.id, second.id])
+
+    def test_after_destroying(self):
+        main = interpreters.get_current()
+        first = interpreters.create()
+        second = interpreters.create()
+        first.close()
+
+        ids = []
+        for interp in interpreters.list_all():
+            ids.append(interp.id)
+
+        self.assertEqual(ids, [main.id, second.id])
+
+    def test_idempotent(self):
+        main = interpreters.get_current()
+        first = interpreters.create()
+        second = interpreters.create()
+        expected = [main, first, second]
+
+        actual = interpreters.list_all()
+
+        self.assertEqual(actual, expected)
+        for interp1, interp2 in zip(actual, expected):
+            self.assertIs(interp1, interp2)
+
+
+class InterpreterObjectTests(TestBase):
+
+    def test_init_int(self):
+        interpid = interpreters.get_current().id
+        interp = interpreters.Interpreter(interpid)
+        self.assertEqual(interp.id, interpid)
+
+    def test_init_interpreter_id(self):
+        interpid = interpreters.get_current()._id
+        interp = interpreters.Interpreter(interpid)
+        self.assertEqual(interp._id, interpid)
+
+    def test_init_unsupported(self):
+        actualid = interpreters.get_current().id
+        for interpid in [
+            str(actualid),
+            float(actualid),
+            object(),
+            None,
+            '',
+        ]:
+            with self.subTest(repr(interpid)):
+                with self.assertRaises(TypeError):
+                    interpreters.Interpreter(interpid)
+
+    def test_idempotent(self):
+        main = interpreters.get_main()
+        interp = interpreters.Interpreter(main.id)
+        self.assertIs(interp, main)
+
+    def test_init_does_not_exist(self):
+        with self.assertRaises(InterpreterNotFoundError):
+            interpreters.Interpreter(1_000_000)
+
+    def test_init_bad_id(self):
+        with self.assertRaises(ValueError):
+            interpreters.Interpreter(-1)
+
+    def test_id_type(self):
+        main = interpreters.get_main()
+        current = interpreters.get_current()
+        interp = interpreters.create()
+        self.assertIsInstance(main.id, int)
+        self.assertIsInstance(current.id, int)
+        self.assertIsInstance(interp.id, int)
+
+    def test_id_readonly(self):
+        interp = interpreters.create()
+        with self.assertRaises(AttributeError):
+            interp.id = 1_000_000
+
+    def test_hashable(self):
+        interp = interpreters.create()
+        expected = hash(interp.id)
+        actual = hash(interp)
+        self.assertEqual(actual, expected)
+
+    def test_equality(self):
+        interp1 = interpreters.create()
+        interp2 = interpreters.create()
+        self.assertEqual(interp1, interp1)
+        self.assertNotEqual(interp1, interp2)
+
+
+class TestInterpreterIsRunning(TestBase):
+
+    def test_main(self):
+        main = interpreters.get_main()
+        self.assertTrue(main.is_running())
+
+    @unittest.skip('Fails on FreeBSD')
+    def test_subinterpreter(self):
+        interp = interpreters.create()
+        self.assertFalse(interp.is_running())
+
+        with _running(interp):
+            self.assertTrue(interp.is_running())
+        self.assertFalse(interp.is_running())
+
+    def test_finished(self):
+        r, w = self.pipe()
+        interp = interpreters.create()
+        interp.exec_sync(f"""if True:
+            import os
+            os.write({w}, b'x')
+            """)
+        self.assertFalse(interp.is_running())
+        self.assertEqual(os.read(r, 1), b'x')
+
+    def test_from_subinterpreter(self):
+        interp = interpreters.create()
+        out = _run_output(interp, dedent(f"""
+            import _xxsubinterpreters as _interpreters
+            if _interpreters.is_running({interp.id}):
+                print(True)
+            else:
+                print(False)
+            """))
+        self.assertEqual(out.strip(), 'True')
+
+    def test_already_destroyed(self):
+        interp = interpreters.create()
+        interp.close()
+        with self.assertRaises(InterpreterNotFoundError):
+            interp.is_running()
+
+    def test_with_only_background_threads(self):
+        r_interp, w_interp = self.pipe()
+        r_thread, w_thread = self.pipe()
+
+        DONE = b'D'
+        FINISHED = b'F'
+
+        interp = interpreters.create()
+        interp.exec_sync(f"""if True:
+            import os
+            import threading
+
+            def task():
+                v = os.read({r_thread}, 1)
+                assert v == {DONE!r}
+                os.write({w_interp}, {FINISHED!r})
+            t = threading.Thread(target=task)
+            t.start()
+            """)
+        self.assertFalse(interp.is_running())
+
+        os.write(w_thread, DONE)
+        interp.exec_sync('t.join()')
+        self.assertEqual(os.read(r_interp, 1), FINISHED)
+
+
+class TestInterpreterClose(TestBase):
+
+    def test_basic(self):
+        main = interpreters.get_main()
+        interp1 = interpreters.create()
+        interp2 = interpreters.create()
+        interp3 = interpreters.create()
+        self.assertEqual(set(interpreters.list_all()),
+                         {main, interp1, interp2, interp3})
+        interp2.close()
+        self.assertEqual(set(interpreters.list_all()),
+                         {main, interp1, interp3})
+
+    def test_all(self):
+        before = set(interpreters.list_all())
+        interps = set()
+        for _ in range(3):
+            interp = interpreters.create()
+            interps.add(interp)
+        self.assertEqual(set(interpreters.list_all()), before | interps)
+        for interp in interps:
+            interp.close()
+        self.assertEqual(set(interpreters.list_all()), before)
+
+    def test_main(self):
+        main, = interpreters.list_all()
+        with self.assertRaises(RuntimeError):
+            main.close()
+
+        def f():
+            with self.assertRaises(RuntimeError):
+                main.close()
+
+        t = threading.Thread(target=f)
+        t.start()
+        t.join()
+
+    def test_already_destroyed(self):
+        interp = interpreters.create()
+        interp.close()
+        with self.assertRaises(InterpreterNotFoundError):
+            interp.close()
+
+    def test_from_current(self):
+        main, = interpreters.list_all()
+        interp = interpreters.create()
+        out = _run_output(interp, dedent(f"""
+            from test.support import interpreters
+            interp = interpreters.Interpreter({interp.id})
+            try:
+                interp.close()
+            except RuntimeError:
+                print('failed')
+            """))
+        self.assertEqual(out.strip(), 'failed')
+        self.assertEqual(set(interpreters.list_all()), {main, interp})
+
+    def test_from_sibling(self):
+        main, = interpreters.list_all()
+        interp1 = interpreters.create()
+        interp2 = interpreters.create()
+        self.assertEqual(set(interpreters.list_all()),
+                         {main, interp1, interp2})
+        interp1.exec_sync(dedent(f"""
+            from test.support import interpreters
+            interp2 = interpreters.Interpreter({interp2.id})
+            interp2.close()
+            interp3 = interpreters.create()
+            interp3.close()
+            """))
+        self.assertEqual(set(interpreters.list_all()), {main, interp1})
+
+    def test_from_other_thread(self):
+        interp = interpreters.create()
+        def f():
+            interp.close()
+
+        t = threading.Thread(target=f)
+        t.start()
+        t.join()
+
+    @unittest.skip('Fails on FreeBSD')
+    def test_still_running(self):
+        main, = interpreters.list_all()
+        interp = interpreters.create()
+        with _running(interp):
+            with self.assertRaises(RuntimeError):
+                interp.close()
+            self.assertTrue(interp.is_running())
+
+    def test_subthreads_still_running(self):
+        r_interp, w_interp = self.pipe()
+        r_thread, w_thread = self.pipe()
+
+        FINISHED = b'F'
+
+        interp = interpreters.create()
+        interp.exec_sync(f"""if True:
+            import os
+            import threading
+            import time
+
+            done = False
+
+            def notify_fini():
+                global done
+                done = True
+                t.join()
+            threading._register_atexit(notify_fini)
+
+            def task():
+                while not done:
+                    time.sleep(0.1)
+                os.write({w_interp}, {FINISHED!r})
+            t = threading.Thread(target=task)
+            t.start()
+            """)
+        interp.close()
+
+        self.assertEqual(os.read(r_interp, 1), FINISHED)
+
+
+class TestInterpreterExecSync(TestBase):
+
+    def test_success(self):
+        interp = interpreters.create()
+        script, file = _captured_script('print("it worked!", end="")')
+        with file:
+            interp.exec_sync(script)
+            out = file.read()
+
+        self.assertEqual(out, 'it worked!')
+
+    def test_failure(self):
+        interp = interpreters.create()
+        with self.assertRaises(interpreters.ExecFailure):
+            interp.exec_sync('raise Exception')
+
+    def test_in_thread(self):
+        interp = interpreters.create()
+        script, file = _captured_script('print("it worked!", end="")')
+        with file:
+            def f():
+                interp.exec_sync(script)
+
+            t = threading.Thread(target=f)
+            t.start()
+            t.join()
+            out = file.read()
+
+        self.assertEqual(out, 'it worked!')
+
+    @support.requires_fork()
+    def test_fork(self):
+        interp = interpreters.create()
+        import tempfile
+        with tempfile.NamedTemporaryFile('w+', encoding='utf-8') as file:
+            file.write('')
+            file.flush()
+
+            expected = 'spam spam spam spam spam'
+            script = dedent(f"""
+                import os
+                try:
+                    os.fork()
+                except RuntimeError:
+                    with open('{file.name}', 'w', encoding='utf-8') as out:
+                        out.write('{expected}')
+                """)
+            interp.exec_sync(script)
+
+            file.seek(0)
+            content = file.read()
+            self.assertEqual(content, expected)
+
+    @unittest.skip('Fails on FreeBSD')
+    def test_already_running(self):
+        interp = interpreters.create()
+        with _running(interp):
+            with self.assertRaises(RuntimeError):
+                interp.exec_sync('print("spam")')
+
+    def test_bad_script(self):
+        interp = interpreters.create()
+        with self.assertRaises(TypeError):
+            interp.exec_sync(10)
+
+    def test_bytes_for_script(self):
+        interp = interpreters.create()
+        with self.assertRaises(TypeError):
+            interp.exec_sync(b'print("spam")')
+
+    def test_with_background_threads_still_running(self):
+        r_interp, w_interp = self.pipe()
+        r_thread, w_thread = self.pipe()
+
+        RAN = b'R'
+        DONE = b'D'
+        FINISHED = b'F'
+
+        interp = interpreters.create()
+        interp.exec_sync(f"""if True:
+            import os
+            import threading
+
+            def task():
+                v = os.read({r_thread}, 1)
+                assert v == {DONE!r}
+                os.write({w_interp}, {FINISHED!r})
+            t = threading.Thread(target=task)
+            t.start()
+            os.write({w_interp}, {RAN!r})
+            """)
+        interp.exec_sync(f"""if True:
+            os.write({w_interp}, {RAN!r})
+            """)
+
+        os.write(w_thread, DONE)
+        interp.exec_sync('t.join()')
+        self.assertEqual(os.read(r_interp, 1), RAN)
+        self.assertEqual(os.read(r_interp, 1), RAN)
+        self.assertEqual(os.read(r_interp, 1), FINISHED)
+
+    # test_xxsubinterpreters covers the remaining
+    # Interpreter.exec_sync() behavior.
+
+
+class TestInterpreterRun(TestBase):
+
+    def test_success(self):
+        interp = interpreters.create()
+        script, file = _captured_script('print("it worked!", end="")')
+        with file:
+            t = interp.run(script)
+            t.join()
+            out = file.read()
+
+        self.assertEqual(out, 'it worked!')
+
+    def test_failure(self):
+        caught = False
+        def excepthook(args):
+            nonlocal caught
+            caught = True
+        threading.excepthook = excepthook
+        try:
+            interp = interpreters.create()
+            t = interp.run('raise Exception')
+            t.join()
+
+            self.assertTrue(caught)
+        except BaseException:
+            threading.excepthook = threading.__excepthook__
+
+
+class TestIsShareable(TestBase):
+
+    def test_default_shareables(self):
+        shareables = [
+                # singletons
+                None,
+                # builtin objects
+                b'spam',
+                'spam',
+                10,
+                -10,
+                True,
+                False,
+                100.0,
+                (),
+                (1, ('spam', 'eggs'), True),
+                ]
+        for obj in shareables:
+            with self.subTest(obj):
+                shareable = interpreters.is_shareable(obj)
+                self.assertTrue(shareable)
+
+    def test_not_shareable(self):
+        class Cheese:
+            def __init__(self, name):
+                self.name = name
+            def __str__(self):
+                return self.name
+
+        class SubBytes(bytes):
+            """A subclass of a shareable type."""
+
+        not_shareables = [
+                # singletons
+                NotImplemented,
+                ...,
+                # builtin types and objects
+                type,
+                object,
+                object(),
+                Exception(),
+                # user-defined types and objects
+                Cheese,
+                Cheese('Wensleydale'),
+                SubBytes(b'spam'),
+                ]
+        for obj in not_shareables:
+            with self.subTest(repr(obj)):
+                self.assertFalse(
+                    interpreters.is_shareable(obj))
+
+
+if __name__ == '__main__':
+    # Test needs to be a package, so we can do relative imports.
+    unittest.main()
diff --git a/Lib/test/test_interpreters/test_channels.py b/Lib/test/test_interpreters/test_channels.py
new file mode 100644
index 0000000..3c3e188
--- /dev/null
+++ b/Lib/test/test_interpreters/test_channels.py
@@ -0,0 +1,328 @@
+import threading
+from textwrap import dedent
+import unittest
+import time
+
+from test.support import import_helper
+# Raise SkipTest if subinterpreters not supported.
+_channels = import_helper.import_module('_xxinterpchannels')
+from test.support import interpreters
+from test.support.interpreters import channels
+from .utils import _run_output, TestBase
+
+
+class TestChannels(TestBase):
+
+    def test_create(self):
+        r, s = channels.create()
+        self.assertIsInstance(r, channels.RecvChannel)
+        self.assertIsInstance(s, channels.SendChannel)
+
+    def test_list_all(self):
+        self.assertEqual(channels.list_all(), [])
+        created = set()
+        for _ in range(3):
+            ch = channels.create()
+            created.add(ch)
+        after = set(channels.list_all())
+        self.assertEqual(after, created)
+
+    def test_shareable(self):
+        rch, sch = channels.create()
+
+        self.assertTrue(
+            interpreters.is_shareable(rch))
+        self.assertTrue(
+            interpreters.is_shareable(sch))
+
+        sch.send_nowait(rch)
+        sch.send_nowait(sch)
+        rch2 = rch.recv()
+        sch2 = rch.recv()
+
+        self.assertEqual(rch2, rch)
+        self.assertEqual(sch2, sch)
+
+    def test_is_closed(self):
+        rch, sch = channels.create()
+        rbefore = rch.is_closed
+        sbefore = sch.is_closed
+        rch.close()
+        rafter = rch.is_closed
+        safter = sch.is_closed
+
+        self.assertFalse(rbefore)
+        self.assertFalse(sbefore)
+        self.assertTrue(rafter)
+        self.assertTrue(safter)
+
+
+class TestRecvChannelAttrs(TestBase):
+
+    def test_id_type(self):
+        rch, _ = channels.create()
+        self.assertIsInstance(rch.id, _channels.ChannelID)
+
+    def test_custom_id(self):
+        rch = channels.RecvChannel(1)
+        self.assertEqual(rch.id, 1)
+
+        with self.assertRaises(TypeError):
+            channels.RecvChannel('1')
+
+    def test_id_readonly(self):
+        rch = channels.RecvChannel(1)
+        with self.assertRaises(AttributeError):
+            rch.id = 2
+
+    def test_equality(self):
+        ch1, _ = channels.create()
+        ch2, _ = channels.create()
+        self.assertEqual(ch1, ch1)
+        self.assertNotEqual(ch1, ch2)
+
+
+class TestSendChannelAttrs(TestBase):
+
+    def test_id_type(self):
+        _, sch = channels.create()
+        self.assertIsInstance(sch.id, _channels.ChannelID)
+
+    def test_custom_id(self):
+        sch = channels.SendChannel(1)
+        self.assertEqual(sch.id, 1)
+
+        with self.assertRaises(TypeError):
+            channels.SendChannel('1')
+
+    def test_id_readonly(self):
+        sch = channels.SendChannel(1)
+        with self.assertRaises(AttributeError):
+            sch.id = 2
+
+    def test_equality(self):
+        _, ch1 = channels.create()
+        _, ch2 = channels.create()
+        self.assertEqual(ch1, ch1)
+        self.assertNotEqual(ch1, ch2)
+
+
+class TestSendRecv(TestBase):
+
+    def test_send_recv_main(self):
+        r, s = channels.create()
+        orig = b'spam'
+        s.send_nowait(orig)
+        obj = r.recv()
+
+        self.assertEqual(obj, orig)
+        self.assertIsNot(obj, orig)
+
+    def test_send_recv_same_interpreter(self):
+        interp = interpreters.create()
+        interp.exec_sync(dedent("""
+            from test.support.interpreters import channels
+            r, s = channels.create()
+            orig = b'spam'
+            s.send_nowait(orig)
+            obj = r.recv()
+            assert obj == orig, 'expected: obj == orig'
+            assert obj is not orig, 'expected: obj is not orig'
+            """))
+
+    @unittest.skip('broken (see BPO-...)')
+    def test_send_recv_different_interpreters(self):
+        r1, s1 = channels.create()
+        r2, s2 = channels.create()
+        orig1 = b'spam'
+        s1.send_nowait(orig1)
+        out = _run_output(
+            interpreters.create(),
+            dedent(f"""
+                obj1 = r.recv()
+                assert obj1 == b'spam', 'expected: obj1 == orig1'
+                # When going to another interpreter we get a copy.
+                assert id(obj1) != {id(orig1)}, 'expected: obj1 is not orig1'
+                orig2 = b'eggs'
+                print(id(orig2))
+                s.send_nowait(orig2)
+                """),
+            channels=dict(r=r1, s=s2),
+            )
+        obj2 = r2.recv()
+
+        self.assertEqual(obj2, b'eggs')
+        self.assertNotEqual(id(obj2), int(out))
+
+    def test_send_recv_different_threads(self):
+        r, s = channels.create()
+
+        def f():
+            while True:
+                try:
+                    obj = r.recv()
+                    break
+                except channels.ChannelEmptyError:
+                    time.sleep(0.1)
+            s.send(obj)
+        t = threading.Thread(target=f)
+        t.start()
+
+        orig = b'spam'
+        s.send(orig)
+        obj = r.recv()
+        t.join()
+
+        self.assertEqual(obj, orig)
+        self.assertIsNot(obj, orig)
+
+    def test_send_recv_nowait_main(self):
+        r, s = channels.create()
+        orig = b'spam'
+        s.send_nowait(orig)
+        obj = r.recv_nowait()
+
+        self.assertEqual(obj, orig)
+        self.assertIsNot(obj, orig)
+
+    def test_send_recv_nowait_main_with_default(self):
+        r, _ = channels.create()
+        obj = r.recv_nowait(None)
+
+        self.assertIsNone(obj)
+
+    def test_send_recv_nowait_same_interpreter(self):
+        interp = interpreters.create()
+        interp.exec_sync(dedent("""
+            from test.support.interpreters import channels
+            r, s = channels.create()
+            orig = b'spam'
+            s.send_nowait(orig)
+            obj = r.recv_nowait()
+            assert obj == orig, 'expected: obj == orig'
+            # When going back to the same interpreter we get the same object.
+            assert obj is not orig, 'expected: obj is not orig'
+            """))
+
+    @unittest.skip('broken (see BPO-...)')
+    def test_send_recv_nowait_different_interpreters(self):
+        r1, s1 = channels.create()
+        r2, s2 = channels.create()
+        orig1 = b'spam'
+        s1.send_nowait(orig1)
+        out = _run_output(
+            interpreters.create(),
+            dedent(f"""
+                obj1 = r.recv_nowait()
+                assert obj1 == b'spam', 'expected: obj1 == orig1'
+                # When going to another interpreter we get a copy.
+                assert id(obj1) != {id(orig1)}, 'expected: obj1 is not orig1'
+                orig2 = b'eggs'
+                print(id(orig2))
+                s.send_nowait(orig2)
+                """),
+            channels=dict(r=r1, s=s2),
+            )
+        obj2 = r2.recv_nowait()
+
+        self.assertEqual(obj2, b'eggs')
+        self.assertNotEqual(id(obj2), int(out))
+
+    def test_recv_timeout(self):
+        r, _ = channels.create()
+        with self.assertRaises(TimeoutError):
+            r.recv(timeout=1)
+
+    def test_recv_channel_does_not_exist(self):
+        ch = channels.RecvChannel(1_000_000)
+        with self.assertRaises(channels.ChannelNotFoundError):
+            ch.recv()
+
+    def test_send_channel_does_not_exist(self):
+        ch = channels.SendChannel(1_000_000)
+        with self.assertRaises(channels.ChannelNotFoundError):
+            ch.send(b'spam')
+
+    def test_recv_nowait_channel_does_not_exist(self):
+        ch = channels.RecvChannel(1_000_000)
+        with self.assertRaises(channels.ChannelNotFoundError):
+            ch.recv_nowait()
+
+    def test_send_nowait_channel_does_not_exist(self):
+        ch = channels.SendChannel(1_000_000)
+        with self.assertRaises(channels.ChannelNotFoundError):
+            ch.send_nowait(b'spam')
+
+    def test_recv_nowait_empty(self):
+        ch, _ = channels.create()
+        with self.assertRaises(channels.ChannelEmptyError):
+            ch.recv_nowait()
+
+    def test_recv_nowait_default(self):
+        default = object()
+        rch, sch = channels.create()
+        obj1 = rch.recv_nowait(default)
+        sch.send_nowait(None)
+        sch.send_nowait(1)
+        sch.send_nowait(b'spam')
+        sch.send_nowait(b'eggs')
+        obj2 = rch.recv_nowait(default)
+        obj3 = rch.recv_nowait(default)
+        obj4 = rch.recv_nowait()
+        obj5 = rch.recv_nowait(default)
+        obj6 = rch.recv_nowait(default)
+
+        self.assertIs(obj1, default)
+        self.assertIs(obj2, None)
+        self.assertEqual(obj3, 1)
+        self.assertEqual(obj4, b'spam')
+        self.assertEqual(obj5, b'eggs')
+        self.assertIs(obj6, default)
+
+    def test_send_buffer(self):
+        buf = bytearray(b'spamspamspam')
+        obj = None
+        rch, sch = channels.create()
+
+        def f():
+            nonlocal obj
+            while True:
+                try:
+                    obj = rch.recv()
+                    break
+                except channels.ChannelEmptyError:
+                    time.sleep(0.1)
+        t = threading.Thread(target=f)
+        t.start()
+
+        sch.send_buffer(buf)
+        t.join()
+
+        self.assertIsNot(obj, buf)
+        self.assertIsInstance(obj, memoryview)
+        self.assertEqual(obj, buf)
+
+        buf[4:8] = b'eggs'
+        self.assertEqual(obj, buf)
+        obj[4:8] = b'ham.'
+        self.assertEqual(obj, buf)
+
+    def test_send_buffer_nowait(self):
+        buf = bytearray(b'spamspamspam')
+        rch, sch = channels.create()
+        sch.send_buffer_nowait(buf)
+        obj = rch.recv()
+
+        self.assertIsNot(obj, buf)
+        self.assertIsInstance(obj, memoryview)
+        self.assertEqual(obj, buf)
+
+        buf[4:8] = b'eggs'
+        self.assertEqual(obj, buf)
+        obj[4:8] = b'ham.'
+        self.assertEqual(obj, buf)
+
+
+if __name__ == '__main__':
+    # Test needs to be a package, so we can do relative imports.
+    unittest.main()
diff --git a/Lib/test/test_interpreters/test_lifecycle.py b/Lib/test/test_interpreters/test_lifecycle.py
new file mode 100644
index 0000000..c2917d8
--- /dev/null
+++ b/Lib/test/test_interpreters/test_lifecycle.py
@@ -0,0 +1,189 @@
+import contextlib
+import json
+import os
+import os.path
+import sys
+from textwrap import dedent
+import unittest
+
+from test import support
+from test.support import import_helper
+from test.support import os_helper
+# Raise SkipTest if subinterpreters not supported.
+import_helper.import_module('_xxsubinterpreters')
+from .utils import TestBase
+
+
+class StartupTests(TestBase):
+
+    # We want to ensure the initial state of subinterpreters
+    # matches expectations.
+
+    _subtest_count = 0
+
+    @contextlib.contextmanager
+    def subTest(self, *args):
+        with super().subTest(*args) as ctx:
+            self._subtest_count += 1
+            try:
+                yield ctx
+            finally:
+                if self._debugged_in_subtest:
+                    if self._subtest_count == 1:
+                        # The first subtest adds a leading newline, so we
+                        # compensate here by not printing a trailing newline.
+                        print('### end subtest debug ###', end='')
+                    else:
+                        print('### end subtest debug ###')
+                self._debugged_in_subtest = False
+
+    def debug(self, msg, *, header=None):
+        if header:
+            self._debug(f'--- {header} ---')
+            if msg:
+                if msg.endswith(os.linesep):
+                    self._debug(msg[:-len(os.linesep)])
+                else:
+                    self._debug(msg)
+                    self._debug('<no newline>')
+            self._debug('------')
+        else:
+            self._debug(msg)
+
+    _debugged = False
+    _debugged_in_subtest = False
+    def _debug(self, msg):
+        if not self._debugged:
+            print()
+            self._debugged = True
+        if self._subtest is not None:
+            if True:
+                if not self._debugged_in_subtest:
+                    self._debugged_in_subtest = True
+                    print('### start subtest debug ###')
+                print(msg)
+        else:
+            print(msg)
+
+    def create_temp_dir(self):
+        import tempfile
+        tmp = tempfile.mkdtemp(prefix='test_interpreters_')
+        tmp = os.path.realpath(tmp)
+        self.addCleanup(os_helper.rmtree, tmp)
+        return tmp
+
+    def write_script(self, *path, text):
+        filename = os.path.join(*path)
+        dirname = os.path.dirname(filename)
+        if dirname:
+            os.makedirs(dirname, exist_ok=True)
+        with open(filename, 'w', encoding='utf-8') as outfile:
+            outfile.write(dedent(text))
+        return filename
+
+    @support.requires_subprocess()
+    def run_python(self, argv, *, cwd=None):
+        # This method is inspired by
+        # EmbeddingTestsMixin.run_embedded_interpreter() in test_embed.py.
+        import shlex
+        import subprocess
+        if isinstance(argv, str):
+            argv = shlex.split(argv)
+        argv = [sys.executable, *argv]
+        try:
+            proc = subprocess.run(
+                argv,
+                cwd=cwd,
+                capture_output=True,
+                text=True,
+            )
+        except Exception as exc:
+            self.debug(f'# cmd: {shlex.join(argv)}')
+            if isinstance(exc, FileNotFoundError) and not exc.filename:
+                if os.path.exists(argv[0]):
+                    exists = 'exists'
+                else:
+                    exists = 'does not exist'
+                self.debug(f'{argv[0]} {exists}')
+            raise  # re-raise
+        assert proc.stderr == '' or proc.returncode != 0, proc.stderr
+        if proc.returncode != 0 and support.verbose:
+            self.debug(f'# python3 {shlex.join(argv[1:])} failed:')
+            self.debug(proc.stdout, header='stdout')
+            self.debug(proc.stderr, header='stderr')
+        self.assertEqual(proc.returncode, 0)
+        self.assertEqual(proc.stderr, '')
+        return proc.stdout
+
+    def test_sys_path_0(self):
+        # The main interpreter's sys.path[0] should be used by subinterpreters.
+        script = '''
+            import sys
+            from test.support import interpreters
+
+            orig = sys.path[0]
+
+            interp = interpreters.create()
+            interp.exec_sync(f"""if True:
+                import json
+                import sys
+                print(json.dumps({{
+                    'main': {orig!r},
+                    'sub': sys.path[0],
+                }}, indent=4), flush=True)
+                """)
+            '''
+        # <tmp>/
+        #   pkg/
+        #     __init__.py
+        #     __main__.py
+        #     script.py
+        #   script.py
+        cwd = self.create_temp_dir()
+        self.write_script(cwd, 'pkg', '__init__.py', text='')
+        self.write_script(cwd, 'pkg', '__main__.py', text=script)
+        self.write_script(cwd, 'pkg', 'script.py', text=script)
+        self.write_script(cwd, 'script.py', text=script)
+
+        cases = [
+            ('script.py', cwd),
+            ('-m script', cwd),
+            ('-m pkg', cwd),
+            ('-m pkg.script', cwd),
+            ('-c "import script"', ''),
+        ]
+        for argv, expected in cases:
+            with self.subTest(f'python3 {argv}'):
+                out = self.run_python(argv, cwd=cwd)
+                data = json.loads(out)
+                sp0_main, sp0_sub = data['main'], data['sub']
+                self.assertEqual(sp0_sub, sp0_main)
+                self.assertEqual(sp0_sub, expected)
+        # XXX Also check them all with the -P cmdline flag?
+
+
+class FinalizationTests(TestBase):
+
+    def test_gh_109793(self):
+        # Make sure finalization finishes and the correct error code
+        # is reported, even when subinterpreters get cleaned up at the end.
+        import subprocess
+        argv = [sys.executable, '-c', '''if True:
+            from test.support import interpreters
+            interp = interpreters.create()
+            raise Exception
+            ''']
+        proc = subprocess.run(argv, capture_output=True, text=True)
+        self.assertIn('Traceback', proc.stderr)
+        if proc.returncode == 0 and support.verbose:
+            print()
+            print("--- cmd unexpected succeeded ---")
+            print(f"stdout:\n{proc.stdout}")
+            print(f"stderr:\n{proc.stderr}")
+            print("------")
+        self.assertEqual(proc.returncode, 1)
+
+
+if __name__ == '__main__':
+    # Test needs to be a package, so we can do relative imports.
+    unittest.main()
diff --git a/Lib/test/test_interpreters/test_queues.py b/Lib/test/test_interpreters/test_queues.py
new file mode 100644
index 0000000..2af90b1
--- /dev/null
+++ b/Lib/test/test_interpreters/test_queues.py
@@ -0,0 +1,233 @@
+import threading
+from textwrap import dedent
+import unittest
+import time
+
+from test.support import import_helper
+# Raise SkipTest if subinterpreters not supported.
+import_helper.import_module('_xxinterpchannels')
+#import_helper.import_module('_xxinterpqueues')
+from test.support import interpreters
+from test.support.interpreters import queues
+from .utils import _run_output, TestBase
+
+
+class QueueTests(TestBase):
+
+    def test_create(self):
+        with self.subTest('vanilla'):
+            queue = queues.create()
+            self.assertEqual(queue.maxsize, 0)
+
+        with self.subTest('small maxsize'):
+            queue = queues.create(3)
+            self.assertEqual(queue.maxsize, 3)
+
+        with self.subTest('big maxsize'):
+            queue = queues.create(100)
+            self.assertEqual(queue.maxsize, 100)
+
+        with self.subTest('no maxsize'):
+            queue = queues.create(0)
+            self.assertEqual(queue.maxsize, 0)
+
+        with self.subTest('negative maxsize'):
+            queue = queues.create(-1)
+            self.assertEqual(queue.maxsize, 0)
+
+        with self.subTest('bad maxsize'):
+            with self.assertRaises(TypeError):
+                queues.create('1')
+
+    @unittest.expectedFailure
+    def test_shareable(self):
+        queue1 = queues.create()
+        queue2 = queues.create()
+        queue1.put(queue2)
+        queue3 = queue1.get()
+        self.assertIs(queue3, queue1)
+
+    def test_id_type(self):
+        queue = queues.create()
+        self.assertIsInstance(queue.id, int)
+
+    def test_custom_id(self):
+        with self.assertRaises(queues.QueueNotFoundError):
+            queues.Queue(1_000_000)
+
+    def test_id_readonly(self):
+        queue = queues.create()
+        with self.assertRaises(AttributeError):
+            queue.id = 1_000_000
+
+    def test_maxsize_readonly(self):
+        queue = queues.create(10)
+        with self.assertRaises(AttributeError):
+            queue.maxsize = 1_000_000
+
+    def test_hashable(self):
+        queue = queues.create()
+        expected = hash(queue.id)
+        actual = hash(queue)
+        self.assertEqual(actual, expected)
+
+    def test_equality(self):
+        queue1 = queues.create()
+        queue2 = queues.create()
+        self.assertEqual(queue1, queue1)
+        self.assertNotEqual(queue1, queue2)
+
+
+class TestQueueOps(TestBase):
+
+    def test_empty(self):
+        queue = queues.create()
+        before = queue.empty()
+        queue.put(None)
+        during = queue.empty()
+        queue.get()
+        after = queue.empty()
+
+        self.assertIs(before, True)
+        self.assertIs(during, False)
+        self.assertIs(after, True)
+
+    def test_full(self):
+        expected = [False, False, False, True, False, False, False]
+        actual = []
+        queue = queues.create(3)
+        for _ in range(3):
+            actual.append(queue.full())
+            queue.put(None)
+        actual.append(queue.full())
+        for _ in range(3):
+            queue.get()
+            actual.append(queue.full())
+
+        self.assertEqual(actual, expected)
+
+    def test_qsize(self):
+        expected = [0, 1, 2, 3, 2, 3, 2, 1, 0, 1, 0]
+        actual = []
+        queue = queues.create()
+        for _ in range(3):
+            actual.append(queue.qsize())
+            queue.put(None)
+        actual.append(queue.qsize())
+        queue.get()
+        actual.append(queue.qsize())
+        queue.put(None)
+        actual.append(queue.qsize())
+        for _ in range(3):
+            queue.get()
+            actual.append(queue.qsize())
+        queue.put(None)
+        actual.append(queue.qsize())
+        queue.get()
+        actual.append(queue.qsize())
+
+        self.assertEqual(actual, expected)
+
+    def test_put_get_main(self):
+        expected = list(range(20))
+        queue = queues.create()
+        for i in range(20):
+            queue.put(i)
+        actual = [queue.get() for _ in range(20)]
+
+        self.assertEqual(actual, expected)
+
+    @unittest.expectedFailure
+    def test_put_timeout(self):
+        queue = queues.create(2)
+        queue.put(None)
+        queue.put(None)
+        with self.assertRaises(queues.QueueFull):
+            queue.put(None, timeout=0.1)
+        queue.get()
+        queue.put(None)
+
+    @unittest.expectedFailure
+    def test_put_nowait(self):
+        queue = queues.create(2)
+        queue.put_nowait(None)
+        queue.put_nowait(None)
+        with self.assertRaises(queues.QueueFull):
+            queue.put_nowait(None)
+        queue.get()
+        queue.put_nowait(None)
+
+    def test_get_timeout(self):
+        queue = queues.create()
+        with self.assertRaises(queues.QueueEmpty):
+            queue.get(timeout=0.1)
+
+    def test_get_nowait(self):
+        queue = queues.create()
+        with self.assertRaises(queues.QueueEmpty):
+            queue.get_nowait()
+
+    def test_put_get_same_interpreter(self):
+        interp = interpreters.create()
+        interp.exec_sync(dedent("""
+            from test.support.interpreters import queues
+            queue = queues.create()
+            orig = b'spam'
+            queue.put(orig)
+            obj = queue.get()
+            assert obj == orig, 'expected: obj == orig'
+            assert obj is not orig, 'expected: obj is not orig'
+            """))
+
+    @unittest.expectedFailure
+    def test_put_get_different_interpreters(self):
+        queue1 = queues.create()
+        queue2 = queues.create()
+        obj1 = b'spam'
+        queue1.put(obj1)
+        out = _run_output(
+            interpreters.create(),
+            dedent(f"""
+                import test.support.interpreters.queue as queues
+                queue1 = queues.Queue({queue1.id})
+                queue2 = queues.Queue({queue2.id})
+                obj = queue1.get()
+                assert obj == b'spam', 'expected: obj == obj1'
+                # When going to another interpreter we get a copy.
+                assert id(obj) != {id(obj1)}, 'expected: obj is not obj1'
+                obj2 = b'eggs'
+                print(id(obj2))
+                queue2.put(obj2)
+                """))
+        obj2 = queue2.get()
+
+        self.assertEqual(obj2, b'eggs')
+        self.assertNotEqual(id(obj2), int(out))
+
+    def test_put_get_different_threads(self):
+        queue1 = queues.create()
+        queue2 = queues.create()
+
+        def f():
+            while True:
+                try:
+                    obj = queue1.get(timeout=0.1)
+                    break
+                except queues.QueueEmpty:
+                    continue
+            queue2.put(obj)
+        t = threading.Thread(target=f)
+        t.start()
+
+        orig = b'spam'
+        queue1.put(orig)
+        obj = queue2.get()
+        t.join()
+
+        self.assertEqual(obj, orig)
+        self.assertIsNot(obj, orig)
+
+
+if __name__ == '__main__':
+    # Test needs to be a package, so we can do relative imports.
+    unittest.main()
diff --git a/Lib/test/test_interpreters/test_stress.py b/Lib/test/test_interpreters/test_stress.py
new file mode 100644
index 0000000..3cc570b
--- /dev/null
+++ b/Lib/test/test_interpreters/test_stress.py
@@ -0,0 +1,38 @@
+import threading
+import unittest
+
+from test import support
+from test.support import import_helper
+from test.support import threading_helper
+# Raise SkipTest if subinterpreters not supported.
+import_helper.import_module('_xxsubinterpreters')
+from test.support import interpreters
+from .utils import TestBase
+
+
+class StressTests(TestBase):
+
+    # In these tests we generally want a lot of interpreters,
+    # but not so many that any test takes too long.
+
+    @support.requires_resource('cpu')
+    def test_create_many_sequential(self):
+        alive = []
+        for _ in range(100):
+            interp = interpreters.create()
+            alive.append(interp)
+
+    @support.requires_resource('cpu')
+    def test_create_many_threaded(self):
+        alive = []
+        def task():
+            interp = interpreters.create()
+            alive.append(interp)
+        threads = (threading.Thread(target=task) for _ in range(200))
+        with threading_helper.start_threads(threads):
+            pass
+
+
+if __name__ == '__main__':
+    # Test needs to be a package, so we can do relative imports.
+    unittest.main()
diff --git a/Lib/test/test_interpreters/utils.py b/Lib/test/test_interpreters/utils.py
new file mode 100644
index 0000000..623c873
--- /dev/null
+++ b/Lib/test/test_interpreters/utils.py
@@ -0,0 +1,73 @@
+import contextlib
+import os
+import threading
+from textwrap import dedent
+import unittest
+
+from test.support import interpreters
+
+
+def _captured_script(script):
+    r, w = os.pipe()
+    indented = script.replace('\n', '\n                ')
+    wrapped = dedent(f"""
+        import contextlib
+        with open({w}, 'w', encoding='utf-8') as spipe:
+            with contextlib.redirect_stdout(spipe):
+                {indented}
+        """)
+    return wrapped, open(r, encoding='utf-8')
+
+
+def clean_up_interpreters():
+    for interp in interpreters.list_all():
+        if interp.id == 0:  # main
+            continue
+        try:
+            interp.close()
+        except RuntimeError:
+            pass  # already destroyed
+
+
+def _run_output(interp, request, channels=None):
+    script, rpipe = _captured_script(request)
+    with rpipe:
+        interp.exec_sync(script, channels=channels)
+        return rpipe.read()
+
+
+@contextlib.contextmanager
+def _running(interp):
+    r, w = os.pipe()
+    def run():
+        interp.exec_sync(dedent(f"""
+            # wait for "signal"
+            with open({r}) as rpipe:
+                rpipe.read()
+            """))
+
+    t = threading.Thread(target=run)
+    t.start()
+
+    yield
+
+    with open(w, 'w') as spipe:
+        spipe.write('done')
+    t.join()
+
+
+class TestBase(unittest.TestCase):
+
+    def pipe(self):
+        def ensure_closed(fd):
+            try:
+                os.close(fd)
+            except OSError:
+                pass
+        r, w = os.pipe()
+        self.addCleanup(lambda: ensure_closed(r))
+        self.addCleanup(lambda: ensure_closed(w))
+        return r, w
+
+    def tearDown(self):
+        clean_up_interpreters()