- issue #6748 intermittent test failures from sockets

- telnetlib tests now use mock sockets for most tests

Lib/test/test_telnetlib.py

 import socket
+import select
 import threading
 import telnetlib
 import time
-import queue
-import sys
-import io
+import contextlib
 
 from unittest import TestCase
 from test import support
 
 HOST = support.HOST
-EOF_sigil = object()
-
-def server(evt, serv, dataq=None, test_done=None):
-    """ Open a tcp server in four steps
-        1) set evt to true to let the parent know we are ready
-        2) [optional] if is not False, write the list of data from dataq.get()
-           to the socket.
-        3) [optional] if test_done is not None, it's an event;  wait
-           for parent to set test_done before closing connection
-        4) set evt to true to let the parent know we're done
-    """
+
+def server(evt, serv):
     serv.listen(5)
     evt.set()
     try:
         conn, addr = serv.accept()
-        if dataq:
-            data = b''
-            new_data = dataq.get(True, 0.5)
-            dataq.task_done()
-            for item in new_data:
-                if item == EOF_sigil:
-                    break
-                if type(item) in [int, float]:
-                    time.sleep(item)
-                else:
-                    data += item
-                written = conn.send(data)
-                data = data[written:]
     except socket.timeout:
         pass
     finally:
-        if test_done is not None:
-            test_done.wait()
         serv.close()
         evt.set()
 
@@ -100,163 +75,159 @@ class GeneralTests(TestCase):
         self.assertEqual(telnet.sock.gettimeout(), 30)
         telnet.sock.close()
 
-def _read_setUp(self):
-    self.evt = threading.Event()
-    self.dataq = queue.Queue()
-    self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-    self.sock.settimeout(3)
-    self.port = support.bind_port(self.sock)
-    self.thread = threading.Thread(target=server, args=(self.evt,self.sock, self.dataq))
-    self.thread.start()
-    self.evt.wait()
-    self.evt.clear()
-    time.sleep(.1)
-
-def _read_tearDown(self):
-    self.evt.wait()
-    self.thread.join()
+class SocketStub(object):
+    ''' a socket proxy that re-defines sendall() '''
+    def __init__(self, reads=[]):
+        self.reads = reads
+        self.writes = []
+        self.block = False
+    def sendall(self, data):
+        self.writes.append(data)
+    def recv(self, size):
+        out = b''
+        while self.reads and len(out) < size:
+            out += self.reads.pop(0)
+        if len(out) > size:
+            self.reads.insert(0, out[size:])
+            out = out[:size]
+        return out
+
+class TelnetAlike(telnetlib.Telnet):
+    def fileno(self):
+        raise NotImplementedError()
+    def close(self): pass
+    def sock_avail(self):
+        return (not self.sock.block)
+    def msg(self, msg, *args):
+        with support.captured_stdout() as out:
+            telnetlib.Telnet.msg(self, msg, *args)
+        self._messages += out.getvalue()
+        return
+
+def new_select(*s_args):
+    block = False
+    for l in s_args:
+        for fob in l:
+            if isinstance(fob, TelnetAlike):
+                block = fob.sock.block
+    if block:
+        return [[], [], []]
+    else:
+        return s_args
+
+@contextlib.contextmanager
+def test_socket(reads):
+    def new_conn(*ignored):
+        return SocketStub(reads)
+    try:
+        old_conn = socket.create_connection
+        socket.create_connection = new_conn
+        yield None
+    finally:
+        socket.create_connection = old_conn
+    return
+
+def test_telnet(reads=[], cls=TelnetAlike):
+    ''' return a telnetlib.Telnet object that uses a SocketStub with
+        reads queued up to be read '''
+    for x in reads:
+        assert type(x) is bytes, x
+    with test_socket(reads):
+        telnet = cls('dummy', 0)
+        telnet._messages = '' # debuglevel output
+    return telnet
 
 class ReadTests(TestCase):
-    setUp = _read_setUp
-    tearDown = _read_tearDown
-
-    # use a similar approach to testing timeouts as test_timeout.py
-    # these will never pass 100% but make the fuzz big enough that it is rare
-    block_long = 0.6
-    block_short = 0.3
-    def test_read_until_A(self):
+    def setUp(self):
+        self.old_select = select.select
+        select.select = new_select
+    def tearDown(self):
+        select.select = self.old_select
+
+    def test_read_until(self):
         """
-        read_until(expected, [timeout])
-          Read until the expected string has been seen, or a timeout is
-          hit (default is no timeout); may block.
+        read_until(expected, timeout=None)
+        test the blocking version of read_util
         """
-        want = [b'x' * 10, b'match', b'y' * 10, EOF_sigil]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
+        want = [b'xxxmatchyyy']
+        telnet = test_telnet(want)
         data = telnet.read_until(b'match')
-        self.assertEqual(data, b''.join(want[:-2]))
+        self.assertEqual(data, b'xxxmatch', msg=(telnet.cookedq, telnet.rawq, telnet.sock.reads))
+
+        reads = [b'x' * 50, b'match', b'y' * 50]
+        expect = b''.join(reads[:-1])
+        telnet = test_telnet(reads)
+        data = telnet.read_until(b'match')
+        self.assertEqual(data, expect)
 
-    def test_read_until_B(self):
-        # test the timeout - it does NOT raise socket.timeout
-        want = [b'hello', self.block_long, b'not seen', EOF_sigil]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        data = telnet.read_until(b'not seen', self.block_short)
-        self.assertEqual(data, want[0])
-        self.assertEqual(telnet.read_all(), b'not seen')
 
-    def test_read_all_A(self):
+    def test_read_all(self):
         """
         read_all()
           Read all data until EOF; may block.
         """
-        want = [b'x' * 500, b'y' * 500, b'z' * 500, EOF_sigil]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
+        reads = [b'x' * 500, b'y' * 500, b'z' * 500]
+        expect = b''.join(reads)
+        telnet = test_telnet(reads)
         data = telnet.read_all()
-        self.assertEqual(data, b''.join(want[:-1]))
+        self.assertEqual(data, expect)
         return
 
-    def _test_blocking(self, func):
-        self.dataq.put([self.block_long, EOF_sigil])
-        self.dataq.join()
-        start = time.time()
-        data = func()
-        self.assertTrue(self.block_short <= time.time() - start)
-
-    def test_read_all_B(self):
-        self._test_blocking(telnetlib.Telnet(HOST, self.port).read_all)
-
-    def test_read_all_C(self):
-        self.dataq.put([EOF_sigil])
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        telnet.read_all()
-        telnet.read_all() # shouldn't raise
-
-    def test_read_some_A(self):
+    def test_read_some(self):
         """
         read_some()
           Read at least one byte or EOF; may block.
         """
         # test 'at least one byte'
-        want = [b'x' * 500, EOF_sigil]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        data = telnet.read_all()
+        telnet = test_telnet([b'x' * 500])
+        data = telnet.read_some()
         self.assertTrue(len(data) >= 1)
-
-    def test_read_some_B(self):
         # test EOF
-        self.dataq.put([EOF_sigil])
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        self.assertEqual(b'', telnet.read_some())
+        telnet = test_telnet()
+        data = telnet.read_some()
+        self.assertEqual(b'', data)
 
-    def test_read_some_C(self):
-        self._test_blocking(telnetlib.Telnet(HOST, self.port).read_some)
-
-    def _test_read_any_eager_A(self, func_name):
+    def _read_eager(self, func_name):
         """
-        read_very_eager()
+        read_*_eager()
           Read all data available already queued or on the socket,
           without blocking.
         """
-        want = [self.block_long, b'x' * 100, b'y' * 100, EOF_sigil]
-        expects = want[1] + want[2]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
+        want = b'x' * 100
+        telnet = test_telnet([want])
         func = getattr(telnet, func_name)
+        telnet.sock.block = True
+        self.assertEqual(b'', func())
+        telnet.sock.block = False
         data = b''
         while True:
             try:
                 data += func()
-                self.assertTrue(expects.startswith(data))
             except EOFError:
                 break
-        self.assertEqual(expects, data)
-
-    def _test_read_any_eager_B(self, func_name):
-        # test EOF
-        self.dataq.put([EOF_sigil])
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        time.sleep(self.block_short)
-        func = getattr(telnet, func_name)
-        self.assertRaises(EOFError, func)
-
-    # read_eager and read_very_eager make the same gaurantees
-    # (they behave differently but we only test the gaurantees)
-    def test_read_very_eager_A(self):
-        self._test_read_any_eager_A('read_very_eager')
-    def test_read_very_eager_B(self):
-        self._test_read_any_eager_B('read_very_eager')
-    def test_read_eager_A(self):
-        self._test_read_any_eager_A('read_eager')
-    def test_read_eager_B(self):
-        self._test_read_any_eager_B('read_eager')
-    # NB -- we need to test the IAC block which is mentioned in the docstring
-    # but not in the module docs
-
-    def _test_read_any_lazy_B(self, func_name):
-        self.dataq.put([EOF_sigil])
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        func = getattr(telnet, func_name)
-        telnet.fill_rawq()
-        self.assertRaises(EOFError, func)
-
-    def test_read_lazy_A(self):
-        want = [b'x' * 100, EOF_sigil]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        time.sleep(self.block_short)
+        self.assertEqual(data, want)
+
+    def test_read_eager(self):
+        # read_eager and read_very_eager make the same gaurantees
+        # (they behave differently but we only test the gaurantees)
+        self._read_eager('read_eager')
+        self._read_eager('read_very_eager')
+        # NB -- we need to test the IAC block which is mentioned in the
+        # docstring but not in the module docs
+
+    def read_very_lazy(self):
+        want = b'x' * 100
+        telnet = test_telnet([want])
+        self.assertEqual(b'', telnet.read_very_lazy())
+        while telnet.sock.reads:
+            telnet.fill_rawq()
+        data = telnet.read_very_lazy()
+        self.assertEqual(want, data)
+        self.assertRaises(EOFError, telnet.read_very_lazy)
+
+    def test_read_lazy(self):
+        want = b'x' * 100
+        telnet = test_telnet([want])
         self.assertEqual(b'', telnet.read_lazy())
         data = b''
         while True:
@@ -267,35 +238,8 @@ class ReadTests(TestCase):
                     telnet.fill_rawq()
             except EOFError:
                 break
-            self.assertTrue(want[0].startswith(data))
-        self.assertEqual(data, want[0])
-
-    def test_read_lazy_B(self):
-        self._test_read_any_lazy_B('read_lazy')
-
-    def test_read_very_lazy_A(self):
-        want = [b'x' * 100, EOF_sigil]
-        self.dataq.put(want)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        time.sleep(self.block_short)
-        self.assertEqual(b'', telnet.read_very_lazy())
-        data = b''
-        while True:
-            try:
-                read_data = telnet.read_very_lazy()
-            except EOFError:
-                break
-            data += read_data
-            if not read_data:
-                telnet.fill_rawq()
-                self.assertEqual(b'', telnet.cookedq)
-                telnet.process_rawq()
-            self.assertTrue(want[0].startswith(data))
-        self.assertEqual(data, want[0])
-
-    def test_read_very_lazy_B(self):
-        self._test_read_any_lazy_B('read_very_lazy')
+            self.assertTrue(want.startswith(data))
+        self.assertEqual(data, want)
 
 class nego_collector(object):
     def __init__(self, sb_getter=None):
@@ -309,91 +253,32 @@ class nego_collector(object):
             sb_data = self.sb_getter()
             self.sb_seen += sb_data
 
-class SocketProxy(object):
-    ''' a socket proxy that re-defines sendall() '''
-    def __init__(self, real_sock):
-        self.socket = real_sock
-        self._raw_sent = b''
-    def __getattr__(self, k):
-        return getattr(self.socket, k)
-    def sendall(self, data):
-        self._raw_sent += data
-        self.socket.sendall(data)
-
-class TelnetSockSendall(telnetlib.Telnet):
-    def open(self, *args, **opts):
-        telnetlib.Telnet.open(self, *args, **opts)
-        self.sock = SocketProxy(self.sock)
+tl = telnetlib
 
 class WriteTests(TestCase):
     '''The only thing that write does is replace each tl.IAC for
     tl.IAC+tl.IAC'''
-    def setUp(self):
-        self.evt = threading.Event()
-        self.test_done = threading.Event()
-        self.dataq = queue.Queue()
-        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        self.sock.settimeout(3)
-        self.port = support.bind_port(self.sock)
-        self.thread = threading.Thread(target=server, args=(
-                self.evt, self.sock, self.dataq, self.test_done))
-        self.thread.start()
-        self.evt.wait()
-        self.evt.clear()
-        time.sleep(.1)
-
-    def tearDown(self):
-        self.test_done.set()
-        self.evt.wait()
-        self.thread.join()
-
-    def _test_write(self, data):
-        self.telnet.sock._raw_sent = b''
-        self.telnet.write(data)
-        after_write = self.telnet.sock._raw_sent
-        self.assertEqual(data.replace(tl.IAC,tl.IAC+tl.IAC),
-                         after_write)
 
     def test_write(self):
-        self.telnet = TelnetSockSendall()
         data_sample = [b'data sample without IAC',
                        b'data sample with' + tl.IAC + b' one IAC',
                        b'a few' + tl.IAC + tl.IAC + b' iacs' + tl.IAC,
                        tl.IAC,
                        b'']
-        self.telnet.open(HOST, self.port)
-        for d in data_sample:
-            self.dataq.put([b''])
-            self._test_write(d)
-        self.telnet.close()
-
-tl = telnetlib
-
-class TelnetDebuglevel(tl.Telnet):
-    ''' Telnet-alike that captures messages written to stdout when
-        debuglevel > 0
-    '''
-    _messages = ''
-    def msg(self, msg, *args):
-        orig_stdout = sys.stdout
-        sys.stdout = fake_stdout = io.StringIO()
-        tl.Telnet.msg(self, msg, *args)
-        self._messages += fake_stdout.getvalue()
-        sys.stdout = orig_stdout
-        return
+        for data in data_sample:
+            telnet = test_telnet()
+            telnet.write(data)
+            written = b''.join(telnet.sock.writes)
+            self.assertEqual(data.replace(tl.IAC,tl.IAC+tl.IAC), written)
 
 class OptionTests(TestCase):
-    setUp = _read_setUp
-    tearDown = _read_tearDown
     # RFC 854 commands
     cmds = [tl.AO, tl.AYT, tl.BRK, tl.EC, tl.EL, tl.GA, tl.IP, tl.NOP]
 
     def _test_command(self, data):
         """ helper for testing IAC + cmd """
-        self.setUp()
-        self.dataq.put(data)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
+        telnet = test_telnet(data)
+        data_len = len(b''.join(data))
         nego = nego_collector()
         telnet.set_option_negotiation_callback(nego.do_nego)
         txt = telnet.read_all()
@@ -401,24 +286,16 @@ class OptionTests(TestCase):
         self.assertTrue(len(cmd) > 0) # we expect at least one command
         self.assertTrue(cmd[:1] in self.cmds)
         self.assertEqual(cmd[1:2], tl.NOOPT)
-        self.assertEqual(len(b''.join(data[:-1])), len(txt + cmd))
+        self.assertEqual(data_len, len(txt + cmd))
         nego.sb_getter = None # break the nego => telnet cycle
-        self.tearDown()
 
     def test_IAC_commands(self):
-        # reset our setup
-        self.dataq.put([EOF_sigil])
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
-        self.tearDown()
-
         for cmd in self.cmds:
-            self._test_command([tl.IAC, cmd, EOF_sigil])
-            self._test_command([b'x' * 100, tl.IAC, cmd, b'y'*100, EOF_sigil])
-            self._test_command([b'x' * 10, tl.IAC, cmd, b'y'*10, EOF_sigil])
+            self._test_command([tl.IAC, cmd])
+            self._test_command([b'x' * 100, tl.IAC, cmd, b'y'*100])
+            self._test_command([b'x' * 10, tl.IAC, cmd, b'y'*10])
         # all at once
-        self._test_command([tl.IAC + cmd for (cmd) in self.cmds] + [EOF_sigil])
-        self.assertEqual(b'', telnet.read_sb_data())
+        self._test_command([tl.IAC + cmd for (cmd) in self.cmds])
 
     def test_SB_commands(self):
         # RFC 855, subnegotiations portion
@@ -427,11 +304,8 @@ class OptionTests(TestCase):
                 tl.IAC + tl.SB + tl.IAC + tl.IAC + b'aa' + tl.IAC + tl.SE,
                 tl.IAC + tl.SB + b'bb' + tl.IAC + tl.IAC + tl.IAC + tl.SE,
                 tl.IAC + tl.SB + b'cc' + tl.IAC + tl.IAC + b'dd' + tl.IAC + tl.SE,
-                EOF_sigil,
                ]
-        self.dataq.put(send)
-        telnet = telnetlib.Telnet(HOST, self.port)
-        self.dataq.join()
+        telnet = test_telnet(send)
         nego = nego_collector(telnet.read_sb_data)
         telnet.set_option_negotiation_callback(nego.do_nego)
         txt = telnet.read_all()
@@ -441,19 +315,6 @@ class OptionTests(TestCase):
         self.assertEqual(b'', telnet.read_sb_data())
         nego.sb_getter = None # break the nego => telnet cycle
 
-    def _test_debuglevel(self, data, expected_msg):
-        """ helper for testing debuglevel messages """
-        self.setUp()
-        self.dataq.put(data + [EOF_sigil])
-        telnet = TelnetDebuglevel(HOST, self.port)
-        telnet.set_debuglevel(1)
-        self.dataq.join()
-        txt = telnet.read_all()
-        self.assertTrue(expected_msg in telnet._messages,
-                        msg=(telnet._messages, expected_msg))
-        telnet.close()
-        self.tearDown()
-
     def test_debuglevel_reads(self):
         # test all the various places that self.msg(...) is called
         given_a_expect_b = [
@@ -467,21 +328,18 @@ class OptionTests(TestCase):
             (tl.IAC + tl.WONT + bytes([1]), ": IAC WONT 1\n"),
            ]
         for a, b in given_a_expect_b:
-            self._test_debuglevel([a, EOF_sigil], b)
+            telnet = test_telnet([a])
+            telnet.set_debuglevel(1)
+            txt = telnet.read_all()
+            self.assertTrue(b in telnet._messages)
         return
 
     def test_debuglevel_write(self):
-        self.setUp()
-        telnet = TelnetDebuglevel(HOST, self.port)
+        telnet = test_telnet()
         telnet.set_debuglevel(1)
-        self.dataq.put([b'', EOF_sigil])
-        self.dataq.join()
         telnet.write(b'xxx')
         expected = "send b'xxx'\n"
-        self.assertTrue(expected in telnet._messages,
-                        msg=(telnet._messages, expected))
-        telnet.close()
-        self.tearDown()
+        self.assertTrue(expected in telnet._messages)
 
 def test_main(verbose=None):
     support.run_unittest(GeneralTests, ReadTests, WriteTests, OptionTests)