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bpo-31158: Fix nondeterministic read in test_pty (#3808) 

* bpo-31158: Fix nondeterministic read in test_pty

* Reuse existing readline implementation from io.

Thx to @pitrou

* Updated comment

Ideally, this commit is fixuped into the previous commit. Since there is
already a comment on github, I won't rebase.
This commit is contained in:
Cornelius Diekmann 2017-10-02 11:39:55 +02:00 committed by Victor Stinner
parent b75a228af8
commit e6f62f69f0
1 changed files with 19 additions and 2 deletions
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21
Lib/test/test_pty.py
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@ -10,6 +10,7 @@ import sys
import select
import signal
import socket
import io # readline
import unittest
TEST_STRING_1 = b"I wish to buy a fish license.\n"
@ -23,6 +24,16 @@ else:
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 figure out
@ -43,6 +54,12 @@ 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.
@ -94,14 +111,14 @@ class PtyTest(unittest.TestCase):
debug("Writing to slave_fd")
os.write(slave_fd, TEST_STRING_1)
s1 = os.read(master_fd, 1024)
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:])
s2 = os.read(master_fd, 1024)
s2 = _readline(master_fd)
self.assertEqual(b'For my pet fish, Eric.\n', normalize_output(s2))
os.close(slave_fd)