https://github.com/python/cpython/commit/20cbc1d29facead32c2da06c81a09af0e05... commit: 20cbc1d29facead32c2da06c81a09af0e057015c branch: 2.7 author: Victor Stinner <victor.stinner@gmail.com> committer: GitHub <noreply@github.com> date: 2017-10-02T02:58:09-07:00 summary: bpo-31158: Fix nondeterministic read in test_pty (#3808) (#3853) (cherry picked from commit e6f62f69f07892b993910ff03c9db3ffa5cb9ca5) files: M Lib/test/test_pty.py 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)