diff --git a/Lib/pty.py b/Lib/pty.py
index 8d8ce40df54..1d97994abef 100644
--- a/Lib/pty.py
+++ b/Lib/pty.py
@@ -40,6 +40,9 @@ def master_open():
     Open a pty master and return the fd, and the filename of the slave end.
     Deprecated, use openpty() instead."""
 
+    import warnings
+    warnings.warn("Use pty.openpty() instead.", DeprecationWarning, stacklevel=2)  # Remove API in 3.14
+
     try:
         master_fd, slave_fd = os.openpty()
     except (AttributeError, OSError):
@@ -69,6 +72,9 @@ def slave_open(tty_name):
     opened filedescriptor.
     Deprecated, use openpty() instead."""
 
+    import warnings
+    warnings.warn("Use pty.openpty() instead.", DeprecationWarning, stacklevel=2)  # Remove API in 3.14
+
     result = os.open(tty_name, os.O_RDWR)
     try:
         from fcntl import ioctl, I_PUSH
@@ -101,32 +107,14 @@ def fork():
     master_fd, slave_fd = openpty()
     pid = os.fork()
     if pid == CHILD:
-        # Establish a new session.
-        os.setsid()
         os.close(master_fd)
-
-        # Slave becomes stdin/stdout/stderr of child.
-        os.dup2(slave_fd, STDIN_FILENO)
-        os.dup2(slave_fd, STDOUT_FILENO)
-        os.dup2(slave_fd, STDERR_FILENO)
-        if slave_fd > STDERR_FILENO:
-            os.close(slave_fd)
-
-        # Explicitly open the tty to make it become a controlling tty.
-        tmp_fd = os.open(os.ttyname(STDOUT_FILENO), os.O_RDWR)
-        os.close(tmp_fd)
+        os.login_tty(slave_fd)
     else:
         os.close(slave_fd)
 
     # Parent and child process.
     return pid, master_fd
 
-def _writen(fd, data):
-    """Write all the data to a descriptor."""
-    while data:
-        n = os.write(fd, data)
-        data = data[n:]
-
 def _read(fd):
     """Default read function."""
     return os.read(fd, 1024)
@@ -136,9 +124,42 @@ def _copy(master_fd, master_read=_read, stdin_read=_read):
     Copies
             pty master -> standard output   (master_read)
             standard input -> pty master    (stdin_read)"""
-    fds = [master_fd, STDIN_FILENO]
-    while fds:
-        rfds, _wfds, _xfds = select(fds, [], [])
+    if os.get_blocking(master_fd):
+        # If we write more than tty/ndisc is willing to buffer, we may block
+        # indefinitely. So we set master_fd to non-blocking temporarily during
+        # the copy operation.
+        os.set_blocking(master_fd, False)
+        try:
+            _copy(master_fd, master_read=master_read, stdin_read=stdin_read)
+        finally:
+            # restore blocking mode for backwards compatibility
+            os.set_blocking(master_fd, True)
+        return
+    high_waterlevel = 4096
+    stdin_avail = master_fd != STDIN_FILENO
+    stdout_avail = master_fd != STDOUT_FILENO
+    i_buf = b''
+    o_buf = b''
+    while 1:
+        rfds = []
+        wfds = []
+        if stdin_avail and len(i_buf) < high_waterlevel:
+            rfds.append(STDIN_FILENO)
+        if stdout_avail and len(o_buf) < high_waterlevel:
+            rfds.append(master_fd)
+        if stdout_avail and len(o_buf) > 0:
+            wfds.append(STDOUT_FILENO)
+        if len(i_buf) > 0:
+            wfds.append(master_fd)
+
+        rfds, wfds, _xfds = select(rfds, wfds, [])
+
+        if STDOUT_FILENO in wfds:
+            try:
+                n = os.write(STDOUT_FILENO, o_buf)
+                o_buf = o_buf[n:]
+            except OSError:
+                stdout_avail = False
 
         if master_fd in rfds:
             # Some OSes signal EOF by returning an empty byte string,
@@ -150,19 +171,22 @@ def _copy(master_fd, master_read=_read, stdin_read=_read):
             if not data:  # Reached EOF.
                 return    # Assume the child process has exited and is
                           # unreachable, so we clean up.
-            else:
-                os.write(STDOUT_FILENO, data)
+            o_buf += data
+
+        if master_fd in wfds:
+            n = os.write(master_fd, i_buf)
+            i_buf = i_buf[n:]
 
-        if STDIN_FILENO in rfds:
+        if stdin_avail and STDIN_FILENO in rfds:
             data = stdin_read(STDIN_FILENO)
             if not data:
-                fds.remove(STDIN_FILENO)
+                stdin_avail = False
             else:
-                _writen(master_fd, data)
+                i_buf += data
 
 def spawn(argv, master_read=_read, stdin_read=_read):
     """Create a spawned process."""
-    if type(argv) == type(''):
+    if isinstance(argv, str):
         argv = (argv,)
     sys.audit('pty.spawn', argv)
 
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 7d8c7a5e016..55585d9ef84 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -2241,6 +2241,7 @@ def child(wpipe):
             expected = terminal_input.decode(sys.stdin.encoding)  # what else?
         self.assertEqual(input_result, expected)
 
+    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_input_tty(self):
         # Test input() functionality when wired to a tty (the code path
         # is different and invokes GNU readline if available).
@@ -2257,17 +2258,20 @@ def skip_if_readline(self):
             self.skipTest("the readline module is loaded")
 
     @unittest.skipUnless(hasattr(sys.stdin, 'detach'), 'TODO: RustPython: requires detach function in TextIOWrapper')
+    @unittest.expectedFailure  # TODO: RUSTPYTHON AssertionError: got 0 lines in pipe but expected 2, child output was: quux
     def test_input_tty_non_ascii(self):
         self.skip_if_readline()
         # Check stdin/stdout encoding is used when invoking PyOS_Readline()
         self.check_input_tty("prompté", b"quux\xe9", "utf-8")
 
     @unittest.skipUnless(hasattr(sys.stdin, 'detach'), 'TODO: RustPython: requires detach function in TextIOWrapper')
+    @unittest.expectedFailure  # TODO: RUSTPYTHON AssertionError: got 0 lines in pipe but expected 2, child output was: quux
     def test_input_tty_non_ascii_unicode_errors(self):
         self.skip_if_readline()
         # Check stdin/stdout error handler is used when invoking PyOS_Readline()
         self.check_input_tty("prompté", b"quux\xe9", "ascii")
 
+    @unittest.expectedFailure  # TODO: RUSTPYTHON AssertionError: got 0 lines in pipe but expected 2, child output was: quux
     def test_input_no_stdout_fileno(self):
         # Issue #24402: If stdin is the original terminal but stdout.fileno()
         # fails, do not use the original stdout file descriptor
diff --git a/Lib/test/test_pty.py b/Lib/test/test_pty.py
index b1c1f6abffb..6d3c47195c6 100644
--- a/Lib/test/test_pty.py
+++ b/Lib/test/test_pty.py
@@ -1,10 +1,16 @@
-from test import support
-from test.support import verbose, reap_children
+import unittest
+from test.support import (
+    is_android, is_apple_mobile, is_emscripten, is_wasi, reap_children, verbose
+)
 from test.support.import_helper import import_module
+from test.support.os_helper import TESTFN, unlink
 
 # Skip these tests if termios is not available
 import_module('termios')
 
+if is_android or is_apple_mobile or is_emscripten or is_wasi:
+    raise unittest.SkipTest("pty is not available on this platform")
+
 import errno
 import os
 import pty
@@ -14,21 +20,12 @@
 import signal
 import socket
 import io # readline
-import unittest
-
-import struct
-import fcntl
 import warnings
 
 TEST_STRING_1 = b"I wish to buy a fish license.\n"
 TEST_STRING_2 = b"For my pet fish, Eric.\n"
 
-try:
-    _TIOCGWINSZ = tty.TIOCGWINSZ
-    _TIOCSWINSZ = tty.TIOCSWINSZ
-    _HAVE_WINSZ = True
-except AttributeError:
-    _HAVE_WINSZ = False
+_HAVE_WINSZ = hasattr(tty, "TIOCGWINSZ") and hasattr(tty, "TIOCSWINSZ")
 
 if verbose:
     def debug(msg):
@@ -82,90 +79,78 @@ def expectedFailureIfStdinIsTTY(fun):
         pass
     return fun
 
-def _get_term_winsz(fd):
-    s = struct.pack("HHHH", 0, 0, 0, 0)
-    return fcntl.ioctl(fd, _TIOCGWINSZ, s)
 
-def _set_term_winsz(fd, winsz):
-    fcntl.ioctl(fd, _TIOCSWINSZ, winsz)
+def write_all(fd, data):
+    written = os.write(fd, data)
+    if written != len(data):
+        # gh-73256, gh-110673: It should never happen, but check just in case
+        raise Exception(f"short write: os.write({fd}, {len(data)} bytes) "
+                        f"wrote {written} bytes")
 
 
 # Marginal testing of pty suite. Cannot do extensive 'do or fail' testing
 # because pty code is not too portable.
 class PtyTest(unittest.TestCase):
     def setUp(self):
-        old_alarm = signal.signal(signal.SIGALRM, self.handle_sig)
-        self.addCleanup(signal.signal, signal.SIGALRM, old_alarm)
-
         old_sighup = signal.signal(signal.SIGHUP, self.handle_sighup)
         self.addCleanup(signal.signal, signal.SIGHUP, old_sighup)
 
-        # isatty() and close() can hang on some platforms. Set an alarm
-        # before running the test to make sure we don't hang forever.
-        self.addCleanup(signal.alarm, 0)
-        signal.alarm(10)
-
-        # Save original stdin window size
-        self.stdin_rows = None
-        self.stdin_cols = None
+        # Save original stdin window size.
+        self.stdin_dim = None
         if _HAVE_WINSZ:
             try:
-                stdin_dim = os.get_terminal_size(pty.STDIN_FILENO)
-                self.stdin_rows = stdin_dim.lines
-                self.stdin_cols = stdin_dim.columns
-                old_stdin_winsz = struct.pack("HHHH", self.stdin_rows,
-                                              self.stdin_cols, 0, 0)
-                self.addCleanup(_set_term_winsz, pty.STDIN_FILENO, old_stdin_winsz)
-            except OSError:
+                self.stdin_dim = tty.tcgetwinsize(pty.STDIN_FILENO)
+                self.addCleanup(tty.tcsetwinsize, pty.STDIN_FILENO,
+                                self.stdin_dim)
+            except tty.error:
                 pass
 
-    def handle_sig(self, sig, frame):
-        self.fail("isatty hung")
-
     @staticmethod
     def handle_sighup(signum, frame):
         pass
 
     @expectedFailureIfStdinIsTTY
+    @unittest.skip('TODO: RUSTPYTHON; "Not runnable. tty.tcgetwinsize" is required to setUp')
     def test_openpty(self):
         try:
             mode = tty.tcgetattr(pty.STDIN_FILENO)
         except tty.error:
-            # not a tty or bad/closed fd
+            # Not a tty or bad/closed fd.
             debug("tty.tcgetattr(pty.STDIN_FILENO) failed")
             mode = None
 
-        new_stdin_winsz = None
-        if self.stdin_rows is not None and self.stdin_cols is not None:
+        new_dim = None
+        if self.stdin_dim:
             try:
                 # Modify pty.STDIN_FILENO window size; we need to
                 # check if pty.openpty() is able to set pty slave
                 # window size accordingly.
-                debug("Setting pty.STDIN_FILENO window size")
-                debug(f"original size: (rows={self.stdin_rows}, cols={self.stdin_cols})")
-                target_stdin_rows = self.stdin_rows + 1
-                target_stdin_cols = self.stdin_cols + 1
-                debug(f"target size: (rows={target_stdin_rows}, cols={target_stdin_cols})")
-                target_stdin_winsz = struct.pack("HHHH", target_stdin_rows,
-                                                 target_stdin_cols, 0, 0)
-                _set_term_winsz(pty.STDIN_FILENO, target_stdin_winsz)
+                debug("Setting pty.STDIN_FILENO window size.")
+                debug(f"original size: (row, col) = {self.stdin_dim}")
+                target_dim = (self.stdin_dim[0] + 1, self.stdin_dim[1] + 1)
+                debug(f"target size: (row, col) = {target_dim}")
+                tty.tcsetwinsize(pty.STDIN_FILENO, target_dim)
 
                 # Were we able to set the window size
                 # of pty.STDIN_FILENO successfully?
-                new_stdin_winsz = _get_term_winsz(pty.STDIN_FILENO)
-                self.assertEqual(new_stdin_winsz, target_stdin_winsz,
+                new_dim = tty.tcgetwinsize(pty.STDIN_FILENO)
+                self.assertEqual(new_dim, target_dim,
                                  "pty.STDIN_FILENO window size unchanged")
-            except OSError:
-                warnings.warn("Failed to set pty.STDIN_FILENO window size")
+            except OSError as e:
+                logging.getLogger(__name__).warning(
+                    "Failed to set pty.STDIN_FILENO window size.", exc_info=e,
+                )
                 pass
 
         try:
             debug("Calling pty.openpty()")
             try:
-                master_fd, slave_fd = pty.openpty(mode, new_stdin_winsz)
+                master_fd, slave_fd, slave_name = pty.openpty(mode, new_dim,
+                                                              True)
             except TypeError:
                 master_fd, slave_fd = pty.openpty()
-            debug(f"Got master_fd '{master_fd}', slave_fd '{slave_fd}'")
+                slave_name = None
+            debug(f"Got {master_fd=}, {slave_fd=}, {slave_name=}")
         except OSError:
             # " An optional feature could not be imported " ... ?
             raise unittest.SkipTest("Pseudo-terminals (seemingly) not functional.")
@@ -181,8 +166,8 @@ def test_openpty(self):
         if mode:
             self.assertEqual(tty.tcgetattr(slave_fd), mode,
                              "openpty() failed to set slave termios")
-        if new_stdin_winsz:
-            self.assertEqual(_get_term_winsz(slave_fd), new_stdin_winsz,
+        if new_dim:
+            self.assertEqual(tty.tcgetwinsize(slave_fd), new_dim,
                              "openpty() failed to set slave window size")
 
         # Ensure the fd is non-blocking in case there's nothing to read.
@@ -200,18 +185,18 @@ def test_openpty(self):
             os.set_blocking(master_fd, blocking)
 
         debug("Writing to slave_fd")
-        os.write(slave_fd, TEST_STRING_1)
+        write_all(slave_fd, TEST_STRING_1)
         s1 = _readline(master_fd)
         self.assertEqual(b'I wish to buy a fish license.\n',
                          normalize_output(s1))
 
         debug("Writing chunked output")
-        os.write(slave_fd, TEST_STRING_2[:5])
-        os.write(slave_fd, TEST_STRING_2[5:])
+        write_all(slave_fd, TEST_STRING_2[:5])
+        write_all(slave_fd, TEST_STRING_2[5:])
         s2 = _readline(master_fd)
         self.assertEqual(b'For my pet fish, Eric.\n', normalize_output(s2))
 
-    @support.requires_fork()
+    @unittest.skip('TODO: RUSTPYTHON; "Not runnable. tty.tcgetwinsize" is required to setUp')
     def test_fork(self):
         debug("calling pty.fork()")
         pid, master_fd = pty.fork()
@@ -294,6 +279,7 @@ def test_fork(self):
             ##else:
             ##    raise TestFailed("Read from master_fd did not raise exception")
 
+    @unittest.skip('TODO: RUSTPYTHON; AttributeError: module "tty" has no attribute "tcgetwinsize"')
     def test_master_read(self):
         # XXX(nnorwitz):  this test leaks fds when there is an error.
         debug("Calling pty.openpty()")
@@ -313,8 +299,28 @@ def test_master_read(self):
 
         self.assertEqual(data, b"")
 
+    @unittest.skip('TODO: RUSTPYTHON; AttributeError: module "tty" has no attribute "tcgetwinsize"')
     def test_spawn_doesnt_hang(self):
-        pty.spawn([sys.executable, '-c', 'print("hi there")'])
+        self.addCleanup(unlink, TESTFN)
+        with open(TESTFN, 'wb') as f:
+            STDOUT_FILENO = 1
+            dup_stdout = os.dup(STDOUT_FILENO)
+            os.dup2(f.fileno(), STDOUT_FILENO)
+            buf = b''
+            def master_read(fd):
+                nonlocal buf
+                data = os.read(fd, 1024)
+                buf += data
+                return data
+            try:
+                pty.spawn([sys.executable, '-c', 'print("hi there")'],
+                          master_read)
+            finally:
+                os.dup2(dup_stdout, STDOUT_FILENO)
+                os.close(dup_stdout)
+        self.assertEqual(buf, b'hi there\r\n')
+        with open(TESTFN, 'rb') as f:
+            self.assertEqual(f.read(), b'hi there\r\n')
 
 class SmallPtyTests(unittest.TestCase):
     """These tests don't spawn children or hang."""
@@ -332,8 +338,8 @@ def setUp(self):
         self.orig_pty_waitpid = pty.waitpid
         self.fds = []  # A list of file descriptors to close.
         self.files = []
-        self.select_rfds_lengths = []
-        self.select_rfds_results = []
+        self.select_input = []
+        self.select_output = []
         self.tcsetattr_mode_setting = None
 
     def tearDown(self):
@@ -368,11 +374,10 @@ def _socketpair(self):
         self.files.extend(socketpair)
         return socketpair
 
-    def _mock_select(self, rfds, wfds, xfds, timeout=0):
+    def _mock_select(self, rfds, wfds, xfds):
         # This will raise IndexError when no more expected calls exist.
-        # This ignores the timeout
-        self.assertEqual(self.select_rfds_lengths.pop(0), len(rfds))
-        return self.select_rfds_results.pop(0), [], []
+        self.assertEqual((rfds, wfds, xfds), self.select_input.pop(0))
+        return self.select_output.pop(0)
 
     def _make_mock_fork(self, pid):
         def mock_fork():
@@ -392,14 +397,16 @@ def test__copy_to_each(self):
         masters = [s.fileno() for s in socketpair]
 
         # Feed data.  Smaller than PIPEBUF.  These writes will not block.
-        os.write(masters[1], b'from master')
-        os.write(write_to_stdin_fd, b'from stdin')
+        write_all(masters[1], b'from master')
+        write_all(write_to_stdin_fd, b'from stdin')
 
-        # Expect two select calls, the last one will cause IndexError
+        # Expect three select calls, the last one will cause IndexError
         pty.select = self._mock_select
-        self.select_rfds_lengths.append(2)
-        self.select_rfds_results.append([mock_stdin_fd, masters[0]])
-        self.select_rfds_lengths.append(2)
+        self.select_input.append(([mock_stdin_fd, masters[0]], [], []))
+        self.select_output.append(([mock_stdin_fd, masters[0]], [], []))
+        self.select_input.append(([mock_stdin_fd, masters[0]], [mock_stdout_fd, masters[0]], []))
+        self.select_output.append(([], [mock_stdout_fd, masters[0]], []))
+        self.select_input.append(([mock_stdin_fd, masters[0]], [], []))
 
         with self.assertRaises(IndexError):
             pty._copy(masters[0])
@@ -410,28 +417,6 @@ def test__copy_to_each(self):
         self.assertEqual(os.read(read_from_stdout_fd, 20), b'from master')
         self.assertEqual(os.read(masters[1], 20), b'from stdin')
 
-    def test__copy_eof_on_all(self):
-        """Test the empty read EOF case on both master_fd and stdin."""
-        read_from_stdout_fd, mock_stdout_fd = self._pipe()
-        pty.STDOUT_FILENO = mock_stdout_fd
-        mock_stdin_fd, write_to_stdin_fd = self._pipe()
-        pty.STDIN_FILENO = mock_stdin_fd
-        socketpair = self._socketpair()
-        masters = [s.fileno() for s in socketpair]
-
-        socketpair[1].close()
-        os.close(write_to_stdin_fd)
-
-        pty.select = self._mock_select
-        self.select_rfds_lengths.append(2)
-        self.select_rfds_results.append([mock_stdin_fd, masters[0]])
-        # We expect that both fds were removed from the fds list as they
-        # both encountered an EOF before the second select call.
-        self.select_rfds_lengths.append(0)
-
-        # We expect the function to return without error.
-        self.assertEqual(pty._copy(masters[0]), None)
-
     def test__restore_tty_mode_normal_return(self):
         """Test that spawn resets the tty mode no when _copy returns normally."""
 
diff --git a/Lib/test/test_tty.py b/Lib/test/test_tty.py
new file mode 100644
index 00000000000..681772fb519
--- /dev/null
+++ b/Lib/test/test_tty.py
@@ -0,0 +1,96 @@
+import os
+import unittest
+from test.support.import_helper import import_module
+
+termios = import_module('termios')
+tty = import_module('tty')
+
+
+@unittest.skipUnless(hasattr(os, 'openpty'), "need os.openpty()")
+class TestTty(unittest.TestCase):
+
+    def setUp(self):
+        master_fd, self.fd = os.openpty()
+        self.addCleanup(os.close, master_fd)
+        self.stream = self.enterContext(open(self.fd, 'wb', buffering=0))
+        self.fd = self.stream.fileno()
+        self.mode = termios.tcgetattr(self.fd)
+        self.addCleanup(termios.tcsetattr, self.fd, termios.TCSANOW, self.mode)
+        self.addCleanup(termios.tcsetattr, self.fd, termios.TCSAFLUSH, self.mode)
+
+    def check_cbreak(self, mode):
+        self.assertEqual(mode[3] & termios.ECHO, 0)
+        self.assertEqual(mode[3] & termios.ICANON, 0)
+        self.assertEqual(mode[6][termios.VMIN], 1)
+        self.assertEqual(mode[6][termios.VTIME], 0)
+
+    def check_raw(self, mode):
+        self.check_cbreak(mode)
+        self.assertEqual(mode[0] & termios.ISTRIP, 0)
+        self.assertEqual(mode[0] & termios.ICRNL, 0)
+        self.assertEqual(mode[1] & termios.OPOST, 0)
+        self.assertEqual(mode[2] & termios.PARENB, termios.CS8 & termios.PARENB)
+        self.assertEqual(mode[2] & termios.CSIZE, termios.CS8 & termios.CSIZE)
+        self.assertEqual(mode[2] & termios.CS8, termios.CS8)
+        self.assertEqual(mode[3] & termios.ECHO, 0)
+        self.assertEqual(mode[3] & termios.ICANON, 0)
+        self.assertEqual(mode[3] & termios.ISIG, 0)
+        self.assertEqual(mode[6][termios.VMIN], 1)
+        self.assertEqual(mode[6][termios.VTIME], 0)
+
+    def test_cfmakeraw(self):
+        mode = termios.tcgetattr(self.fd)
+        self.assertEqual(mode, self.mode)
+        tty.cfmakeraw(mode)
+        self.check_raw(mode)
+        self.assertEqual(mode[4], self.mode[4])
+        self.assertEqual(mode[5], self.mode[5])
+
+    def test_cfmakecbreak(self):
+        mode = termios.tcgetattr(self.fd)
+        self.assertEqual(mode, self.mode)
+        tty.cfmakecbreak(mode)
+        self.check_cbreak(mode)
+        self.assertEqual(mode[1], self.mode[1])
+        self.assertEqual(mode[2], self.mode[2])
+        self.assertEqual(mode[4], self.mode[4])
+        self.assertEqual(mode[5], self.mode[5])
+        mode[tty.IFLAG] |= termios.ICRNL
+        tty.cfmakecbreak(mode)
+        self.assertEqual(mode[tty.IFLAG] & termios.ICRNL, termios.ICRNL,
+                         msg="ICRNL should not be cleared by cbreak")
+        mode[tty.IFLAG] &= ~termios.ICRNL
+        tty.cfmakecbreak(mode)
+        self.assertEqual(mode[tty.IFLAG] & termios.ICRNL, 0,
+                         msg="ICRNL should not be set by cbreak")
+
+    @unittest.expectedFailure # TODO: RUSTPYTHON TypeError: Expected type "int" but "FileIO" found.
+    def test_setraw(self):
+        mode0 = termios.tcgetattr(self.fd)
+        mode1 = tty.setraw(self.fd)
+        self.assertEqual(mode1, mode0)
+        mode2 = termios.tcgetattr(self.fd)
+        self.check_raw(mode2)
+        mode3 = tty.setraw(self.fd, termios.TCSANOW)
+        self.assertEqual(mode3, mode2)
+        tty.setraw(self.stream)
+        tty.setraw(fd=self.fd, when=termios.TCSANOW)
+
+    @unittest.expectedFailure # TODO: RUSTPYTHON TypeError: Expected type "int" but "FileIO" found.
+    def test_setcbreak(self):
+        mode0 = termios.tcgetattr(self.fd)
+        mode1 = tty.setcbreak(self.fd)
+        self.assertEqual(mode1, mode0)
+        mode2 = termios.tcgetattr(self.fd)
+        self.check_cbreak(mode2)
+        ICRNL = termios.ICRNL
+        self.assertEqual(mode2[tty.IFLAG] & ICRNL, mode0[tty.IFLAG] & ICRNL,
+                         msg="ICRNL should not be altered by cbreak")
+        mode3 = tty.setcbreak(self.fd, termios.TCSANOW)
+        self.assertEqual(mode3, mode2)
+        tty.setcbreak(self.stream)
+        tty.setcbreak(fd=self.fd, when=termios.TCSANOW)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/Lib/tty.py b/Lib/tty.py
index a72eb675545..5a49e040042 100644
--- a/Lib/tty.py
+++ b/Lib/tty.py
@@ -4,9 +4,9 @@
 
 from termios import *
 
-__all__ = ["setraw", "setcbreak"]
+__all__ = ["cfmakeraw", "cfmakecbreak", "setraw", "setcbreak"]
 
-# Indexes for termios list.
+# Indices for termios list.
 IFLAG = 0
 OFLAG = 1
 CFLAG = 2
@@ -15,22 +15,59 @@
 OSPEED = 5
 CC = 6
 
-def setraw(fd, when=TCSAFLUSH):
-    """Put terminal into a raw mode."""
-    mode = tcgetattr(fd)
-    mode[IFLAG] = mode[IFLAG] & ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON)
-    mode[OFLAG] = mode[OFLAG] & ~(OPOST)
-    mode[CFLAG] = mode[CFLAG] & ~(CSIZE | PARENB)
-    mode[CFLAG] = mode[CFLAG] | CS8
-    mode[LFLAG] = mode[LFLAG] & ~(ECHO | ICANON | IEXTEN | ISIG)
+def cfmakeraw(mode):
+    """Make termios mode raw."""
+    # Clear all POSIX.1-2017 input mode flags.
+    # See chapter 11 "General Terminal Interface"
+    # of POSIX.1-2017 Base Definitions.
+    mode[IFLAG] &= ~(IGNBRK | BRKINT | IGNPAR | PARMRK | INPCK | ISTRIP |
+                     INLCR | IGNCR | ICRNL | IXON | IXANY | IXOFF)
+
+    # Do not post-process output.
+    mode[OFLAG] &= ~OPOST
+
+    # Disable parity generation and detection; clear character size mask;
+    # let character size be 8 bits.
+    mode[CFLAG] &= ~(PARENB | CSIZE)
+    mode[CFLAG] |= CS8
+
+    # Clear all POSIX.1-2017 local mode flags.
+    mode[LFLAG] &= ~(ECHO | ECHOE | ECHOK | ECHONL | ICANON |
+                     IEXTEN | ISIG | NOFLSH | TOSTOP)
+
+    # POSIX.1-2017, 11.1.7 Non-Canonical Mode Input Processing,
+    # Case B: MIN>0, TIME=0
+    # A pending read shall block until MIN (here 1) bytes are received,
+    # or a signal is received.
+    mode[CC] = list(mode[CC])
     mode[CC][VMIN] = 1
     mode[CC][VTIME] = 0
-    tcsetattr(fd, when, mode)
 
-def setcbreak(fd, when=TCSAFLUSH):
-    """Put terminal into a cbreak mode."""
-    mode = tcgetattr(fd)
-    mode[LFLAG] = mode[LFLAG] & ~(ECHO | ICANON)
+def cfmakecbreak(mode):
+    """Make termios mode cbreak."""
+    # Do not echo characters; disable canonical input.
+    mode[LFLAG] &= ~(ECHO | ICANON)
+
+    # POSIX.1-2017, 11.1.7 Non-Canonical Mode Input Processing,
+    # Case B: MIN>0, TIME=0
+    # A pending read shall block until MIN (here 1) bytes are received,
+    # or a signal is received.
+    mode[CC] = list(mode[CC])
     mode[CC][VMIN] = 1
     mode[CC][VTIME] = 0
-    tcsetattr(fd, when, mode)
+
+def setraw(fd, when=TCSAFLUSH):
+    """Put terminal into raw mode."""
+    mode = tcgetattr(fd)
+    new = list(mode)
+    cfmakeraw(new)
+    tcsetattr(fd, when, new)
+    return mode
+
+def setcbreak(fd, when=TCSAFLUSH):
+    """Put terminal into cbreak mode."""
+    mode = tcgetattr(fd)
+    new = list(mode)
+    cfmakecbreak(new)
+    tcsetattr(fd, when, new)
+    return mode