changeset 45068:8cd18aba5e6c

tests: proof test-stdio.py against buffer fill-up With the previous code, it could in theory happen that the pipe / PTY buffer of the child stdout / stderr fills up and the process never finishes. To prevent that, we read all of the stream before waiting for the end of the process. To ensure that the stream reaches EOF when the child finishes, we must close the parent "copy" of the child stdout / stderr.
author Manuel Jacob <me@manueljacob.de>
date Tue, 07 Jul 2020 11:06:37 +0200
parents 9a062913bab6
children 9172fd511999
files tests/test-stdio.py
diffstat 1 files changed, 25 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- a/tests/test-stdio.py	Thu Jul 09 23:03:34 2020 -0400
+++ b/tests/test-stdio.py	Tue Jul 07 11:06:37 2020 +0200
@@ -5,6 +5,7 @@
 from __future__ import absolute_import
 
 import contextlib
+import errno
 import os
 import subprocess
 import sys
@@ -62,6 +63,23 @@
         yield rwpair
 
 
+def _readall(fd, buffer_size):
+    buf = []
+    while True:
+        try:
+            s = os.read(fd, buffer_size)
+        except OSError as e:
+            if e.errno == errno.EIO:
+                # If the child-facing PTY got closed, reading from the
+                # parent-facing PTY raises EIO.
+                break
+            raise
+        if not s:
+            break
+        buf.append(s)
+    return b''.join(buf)
+
+
 class TestStdio(unittest.TestCase):
     def _test(self, stream, rwpair_generator, expected_output, python_args=[]):
         assert stream in ('stdout', 'stderr')
@@ -76,9 +94,14 @@
                 stdout=child_stream if stream == 'stdout' else None,
                 stderr=child_stream if stream == 'stderr' else None,
             )
-            retcode = proc.wait()
+            try:
+                os.close(child_stream)
+                self.assertEqual(
+                    _readall(stream_receiver, 1024), expected_output
+                )
+            finally:
+                retcode = proc.wait()
             self.assertEqual(retcode, 0)
-            self.assertEqual(os.read(stream_receiver, 1024), expected_output)
 
     def test_stdout_pipes(self):
         self._test('stdout', _pipes, FULLY_BUFFERED)