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5135992164
no longer lose data when an underlying read system call is interrupted. IOError is no longer raised due to a read system call returning EINTR from within these methods.
236 lines
10 KiB
Python
236 lines
10 KiB
Python
# Written to test interrupted system calls interfering with our many buffered
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# IO implementations. http://bugs.python.org/issue12268
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#
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# It was suggested that this code could be merged into test_io and the tests
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# made to work using the same method as the existing signal tests in test_io.
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# I was unable to get single process tests using alarm or setitimer that way
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# to reproduce the EINTR problems. This process based test suite reproduces
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# the problems prior to the issue12268 patch reliably on Linux and OSX.
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# - gregory.p.smith
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import os
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import select
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import signal
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import subprocess
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import sys
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from test.support import run_unittest
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import time
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import unittest
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# Test import all of the things we're about to try testing up front.
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from _io import FileIO
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@unittest.skipUnless(os.name == 'posix', 'tests requires a posix system.')
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class TestFileIOSignalInterrupt(unittest.TestCase):
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def setUp(self):
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self._process = None
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def tearDown(self):
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if self._process and self._process.poll() is None:
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try:
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self._process.kill()
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except OSError:
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pass
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def _generate_infile_setup_code(self):
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"""Returns the infile = ... line of code for the reader process.
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subclasseses should override this to test different IO objects.
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"""
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return ('import _io ;'
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'infile = _io.FileIO(sys.stdin.fileno(), "rb")')
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def fail_with_process_info(self, why, stdout=b'', stderr=b'',
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communicate=True):
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"""A common way to cleanup and fail with useful debug output.
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Kills the process if it is still running, collects remaining output
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and fails the test with an error message including the output.
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Args:
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why: Text to go after "Error from IO process" in the message.
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stdout, stderr: standard output and error from the process so
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far to include in the error message.
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communicate: bool, when True we call communicate() on the process
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after killing it to gather additional output.
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"""
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if self._process.poll() is None:
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time.sleep(0.1) # give it time to finish printing the error.
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try:
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self._process.terminate() # Ensure it dies.
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except OSError:
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pass
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if communicate:
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stdout_end, stderr_end = self._process.communicate()
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stdout += stdout_end
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stderr += stderr_end
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self.fail('Error from IO process %s:\nSTDOUT:\n%sSTDERR:\n%s\n' %
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(why, stdout.decode(), stderr.decode()))
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def _test_reading(self, data_to_write, read_and_verify_code):
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"""Generic buffered read method test harness to validate EINTR behavior.
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Also validates that Python signal handlers are run during the read.
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Args:
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data_to_write: String to write to the child process for reading
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before sending it a signal, confirming the signal was handled,
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writing a final newline and closing the infile pipe.
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read_and_verify_code: Single "line" of code to read from a file
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object named 'infile' and validate the result. This will be
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executed as part of a python subprocess fed data_to_write.
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"""
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infile_setup_code = self._generate_infile_setup_code()
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# Total pipe IO in this function is smaller than the minimum posix OS
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# pipe buffer size of 512 bytes. No writer should block.
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assert len(data_to_write) < 512, 'data_to_write must fit in pipe buf.'
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# Start a subprocess to call our read method while handling a signal.
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self._process = subprocess.Popen(
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[sys.executable, '-u', '-c',
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'import signal, sys ;'
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'signal.signal(signal.SIGINT, '
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'lambda s, f: sys.stderr.write("$\\n")) ;'
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+ infile_setup_code + ' ;' +
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'sys.stderr.write("Worm Sign!\\n") ;'
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+ read_and_verify_code + ' ;' +
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'infile.close()'
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],
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stdin=subprocess.PIPE, stdout=subprocess.PIPE,
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stderr=subprocess.PIPE)
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# Wait for the signal handler to be installed.
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worm_sign = self._process.stderr.read(len(b'Worm Sign!\n'))
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if worm_sign != b'Worm Sign!\n': # See also, Dune by Frank Herbert.
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self.fail_with_process_info('while awaiting a sign',
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stderr=worm_sign)
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self._process.stdin.write(data_to_write)
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signals_sent = 0
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rlist = []
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# We don't know when the read_and_verify_code in our child is actually
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# executing within the read system call we want to interrupt. This
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# loop waits for a bit before sending the first signal to increase
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# the likelihood of that. Implementations without correct EINTR
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# and signal handling usually fail this test.
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while not rlist:
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rlist, _, _ = select.select([self._process.stderr], (), (), 0.05)
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self._process.send_signal(signal.SIGINT)
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signals_sent += 1
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if signals_sent > 200:
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self._process.kill()
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self.fail('reader process failed to handle our signals.')
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# This assumes anything unexpected that writes to stderr will also
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# write a newline. That is true of the traceback printing code.
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signal_line = self._process.stderr.readline()
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if signal_line != b'$\n':
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self.fail_with_process_info('while awaiting signal',
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stderr=signal_line)
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# We append a newline to our input so that a readline call can
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# end on its own before the EOF is seen and so that we're testing
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# the read call that was interrupted by a signal before the end of
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# the data stream has been reached.
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stdout, stderr = self._process.communicate(input=b'\n')
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if self._process.returncode:
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self.fail_with_process_info(
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'exited rc=%d' % self._process.returncode,
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stdout, stderr, communicate=False)
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# PASS!
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# String format for the read_and_verify_code used by read methods.
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_READING_CODE_TEMPLATE = (
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'got = infile.{read_method_name}() ;'
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'expected = {expected!r} ;'
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'assert got == expected, ('
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'"{read_method_name} returned wrong data.\\n"'
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'"got data %r\\nexpected %r" % (got, expected))'
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)
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def test_readline(self):
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"""readline() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello, world!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='readline',
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expected=b'hello, world!\n'))
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def test_readlines(self):
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"""readlines() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello\nworld!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='readlines',
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expected=[b'hello\n', b'world!\n']))
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def test_readall(self):
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"""readall() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello\nworld!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='readall',
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expected=b'hello\nworld!\n'))
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# read() is the same thing as readall().
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self._test_reading(
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data_to_write=b'hello\nworld!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='read',
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expected=b'hello\nworld!\n'))
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class TestBufferedIOSignalInterrupt(TestFileIOSignalInterrupt):
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def _generate_infile_setup_code(self):
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"""Returns the infile = ... line of code to make a BufferedReader."""
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return ('infile = open(sys.stdin.fileno(), "rb") ;'
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'import _io ;assert isinstance(infile, _io.BufferedReader)')
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def test_readall(self):
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"""BufferedReader.read() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello\nworld!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='read',
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expected=b'hello\nworld!\n'))
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class TestTextIOSignalInterrupt(TestFileIOSignalInterrupt):
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def _generate_infile_setup_code(self):
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"""Returns the infile = ... line of code to make a TextIOWrapper."""
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return ('infile = open(sys.stdin.fileno(), "rt", newline=None) ;'
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'import _io ;assert isinstance(infile, _io.TextIOWrapper)')
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def test_readline(self):
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"""readline() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello, world!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='readline',
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expected='hello, world!\n'))
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def test_readlines(self):
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"""readlines() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello\r\nworld!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='readlines',
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expected=['hello\n', 'world!\n']))
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def test_readall(self):
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"""read() must handle signals and not lose data."""
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self._test_reading(
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data_to_write=b'hello\nworld!',
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read_and_verify_code=self._READING_CODE_TEMPLATE.format(
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read_method_name='read',
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expected="hello\nworld!\n"))
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def test_main():
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test_cases = [
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tc for tc in globals().values()
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if isinstance(tc, type) and issubclass(tc, unittest.TestCase)]
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run_unittest(*test_cases)
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if __name__ == '__main__':
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test_main()
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