diff --git a/Lib/test/test_pty.py b/Lib/test/test_pty.py

index bec38c45456..f623aa09620 100644

--- a/Lib/test/test_pty.py

+++ b/Lib/test/test_pty.py

@@ -11,6 +11,7 @@

 import select

 import signal

 import socket

+import io # readline

 import unittest

 TEST_STRING_1 = "I wish to buy a fish license.\n"

@@ -24,6 +25,16 @@ def debug(msg):

         pass

+# Note that os.read() is nondeterministic so we need to be very careful

+# to make the test suite deterministic.  A normal call to os.read() may

+# give us less than expected.

+#

+# Beware, on my Linux system, if I put 'foo\n' into a terminal fd, I get

+# back 'foo\r\n' at the other end.  The behavior depends on the termios

+# setting.  The newline translation may be OS-specific.  To make the

+# test suite deterministic and OS-independent, the functions _readline

+# and normalize_output can be used.

+

 def normalize_output(data):

     # Some operating systems do conversions on newline.  We could possibly

     # fix that by doing the appropriate termios.tcsetattr()s.  I couldn't

@@ -45,6 +56,12 @@ def normalize_output(data):

     return data

+def _readline(fd):

+    """Read one line.  May block forever if no newline is read."""

+    reader = io.FileIO(fd, mode='rb', closefd=False)

+    return reader.readline()

+

+

 # Marginal testing of pty suite. Cannot do extensive 'do or fail' testing

 # because pty code is not too portable.

@@ -97,14 +114,14 @@ def test_basic(self):

         debug("Writing to slave_fd")

         os.write(slave_fd, TEST_STRING_1)

-        s1 = os.read(master_fd, 1024)

+        s1 = _readline(master_fd)

         self.assertEqual('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:])

-        s2 = os.read(master_fd, 1024)

+        s2 = _readline(master_fd)

         self.assertEqual('For my pet fish, Eric.\n', normalize_output(s2))

         os.close(slave_fd)