[Django] #36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when setUpTestData raises and tests are run with –parallel

Django

unread,

Jul 3, 2025, 10:33:00 AMJul 3

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Type: Bug
Soriano Marmol | Component: Testing
Status: new | framework
Version: 5.2 | Severity: Normal
Keywords: tests, parallel, | Triage Stage:
buffer | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Similar issue reported here: https://code.djangoproject.com/ticket/35794

If a test class raises an exception in setUpTestData(), the failure is
reported correctly when tests are executed
• in sequence, or
• in parallel without buffering (--parallel only).

However, running the same suite with both **--parallel and --buffer**
causes the test run to abort with an unrelated AttributeError, and the
original exception is lost.

Minimal reproducer

{{{

# tests/test_issue.py
from django.test import TestCase

class AbortingTest(TestCase):
@classmethod
def setUpTestData(cls):
raise RuntimeError("Boo!")

def test_pass(self):
pass

class AnotherAbortingTest(TestCase):
@classmethod
def setUpTestData(cls):
raise RuntimeError("Boo Too!")

def test_pass(self):
pass
}}}

the errors are reported clearly when running tests in sequence or
--parallel **without --buffer**

{{{
======================================================================
ERROR: setUpClass
(investment.investment.tests.test_issue.AnotherAbortingTest)
----------------------------------------------------------------------
Traceback (most recent call last):
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/suite.py",
line 166, in _handleClassSetUp
setUpClass()
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/test/testcases.py", line 1426, in setUpClass
cls.setUpTestData()
^^^^^^^^^^^^^^^^^
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/Indiana/investment/investment/tests/test_issue.py", line
16, in setUpTestData
raise RuntimeError("Boo Too!")
^^^^^^^^^^^^^^^^^
RuntimeError: Boo Too!

======================================================================
ERROR: setUpClass (investment.investment.tests.test_issue.AbortingTest)
----------------------------------------------------------------------
Traceback (most recent call last):
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/suite.py",
line 166, in _handleClassSetUp
setUpClass()
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/test/testcases.py", line 1426, in setUpClass
cls.setUpTestData()
^^^^^^^^^^^^^^^^^
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/Indiana/investment/investment/tests/test_issue.py", line
7, in setUpTestData
raise RuntimeError("Boo!")
^^^^^^^^^^^^^^^^^
RuntimeError: Boo!

----------------------------------------------------------------------
Ran 0 tests in 4.715s

FAILED (errors=2)
}}}

❌ Fails (parallel **with** buffer)

python manage.py test tests.test_issue --parallel --buffer

{{{
Destroying test database for alias 'default'...
Traceback (most recent call last):
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/Indiana/manage.py", line 34, in <module>
main()
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/Indiana/manage.py", line 29, in main
execute_from_command_line(sys.argv)
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/core/management/__init__.py", line 442, in
execute_from_command_line
utility.execute()
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/core/management/__init__.py", line 436, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/core/management/commands/test.py", line 24, in
run_from_argv
super().run_from_argv(argv)
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/core/management/base.py", line 416, in run_from_argv
self.execute(*args, **cmd_options)
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/core/management/base.py", line 460, in execute
output = self.handle(*args, **options)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/core/management/commands/test.py", line 63, in handle
failures = test_runner.run_tests(test_labels)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/test/runner.py", line 1099, in run_tests
result = self.run_suite(suite)
^^^^^^^^^^^^^^^^^^^^^
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/test/runner.py", line 1026, in run_suite
return runner.run(suite)
^^^^^^^^^^^^^^^^^
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/runner.py",
line 240, in run
test(result)
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/suite.py",
line 84, in __call__
return self.run(*args, **kwds)
^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/test/runner.py", line 562, in run
self.handle_event(result, tests, event)
File "/Users/rafa...@backbase.com/dell/home/rsoriano/repositorios
/docker-indiana/venvs/indiana_3_12/lib/python3.12/site-
packages/django/test/runner.py", line 586, in handle_event
handler(test, *args)
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/runner.py",
line 101, in addError
super(TextTestResult, self).addError(test, err)
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/result.py",
line 17, in inner
return method(self, *args, **kw)
^^^^^^^^^^^^^^^^^^^^^^^^^
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/result.py",
line 116, in addError
self.errors.append((test, self._exc_info_to_string(err, test)))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File
"/opt/homebrew/Cellar/pyt...@3.12/3.12.11/Frameworks/Python.framework/Versions/3.12/lib/python3.12/unittest/result.py",
line 195, in _exc_info_to_string
output = sys.stdout.getvalue()
^^^^^^^^^^^^^^^^^^^
AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue'
}}}

* The traceback contains no reference to the original RuntimeError("Boo!")
/ RuntimeError("Boo Too!").

**Expected behaviour**

With --parallel --buffer the test runner should report the same clear
RuntimeError stack traces shown when buffering is disabled.

**Actual behaviour**

The run aborts with an AttributeError deep inside unittest.result, and the
real test failures are swallowed.

** Additional details **

* tblib installed (latest version == 3.1.0)
* logging => logging.StreamHandler
* Removing either --parallel or --buffer avoids the issue.

Similar issue reported here: https://code.djangoproject.com/ticket/35794
--
Ticket URL: <https://code.djangoproject.com/ticket/36491>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

Django

unread,

Jul 3, 2025, 10:33:31 AMJul 3

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------

Changes (by Rafael Carlos Soriano Marmol):

* Attachment "test_issue.py" added.

Django

unread,

Jul 3, 2025, 10:36:28 AMJul 3

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------

Reporter: rafaelsm_backbase | Owner: (none)

Changes (by rafaelsm_backbase):

* Attachment "issue" added.

Django

unread,

Jul 4, 2025, 4:32:50 AMJul 4

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------

Reporter: Rafael Carlos | Owner: (none)
Soriano Marmol |

Description changed by Rafael Carlos Soriano Marmol:

Old description:

> AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue'
> }}}
>

> * The traceback contains no reference to the original
> RuntimeError("Boo!") / RuntimeError("Boo Too!").
>
> **Expected behaviour**
>
> With --parallel --buffer the test runner should report the same clear
> RuntimeError stack traces shown when buffering is disabled.
>
> **Actual behaviour**
>
> The run aborts with an AttributeError deep inside unittest.result, and
> the real test failures are swallowed.
>
> ** Additional details **
>
> * tblib installed (latest version == 3.1.0)
> * logging => logging.StreamHandler
> * Removing either --parallel or --buffer avoids the issue.
>
> Similar issue reported here: https://code.djangoproject.com/ticket/35794

New description:

AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue'
}}}

* The traceback contains no reference to the original RuntimeError("Boo!")
/ RuntimeError("Boo Too!").

**Expected behaviour**

With --parallel --buffer the test runner should report the same clear
RuntimeError stack traces shown when buffering is disabled.

**Actual behaviour**

The run aborts with an AttributeError deep inside unittest.result, and the
real test failures are swallowed.

** Additional details **

* tblib installed (latest version == 3.1.0)
* logging => logging.StreamHandler
* Removing either --parallel or --buffer avoids the issue.

Similar issue reported here: https://code.djangoproject.com/ticket/35794

Edit:

issue also happens with exceptions inside setUpClass (--parallel --buffer)

{{{
class AbortingTest(TestCase):
@classmethod
def setUpClass(cls):

raise RuntimeError("Boo!")

def test_pass(self):
pass

}}}

--
--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:1>

Django

unread,

Jul 4, 2025, 4:32:57 AMJul 4

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Owner: (none)
Soriano Marmol |
Type: Bug | Status: new
Component: Testing framework | Version: 5.2
Severity: Normal | Resolution:
Keywords: tests, parallel, | Triage Stage:
buffer | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Rafael Carlos Soriano Marmol):

issue also happens with exceptions inside setUpClass (--parallel --buffer)

{{{
class AbortingTest(TestCase):
@classmethod
def setUpClass(cls):
raise RuntimeError("Boo!")

def test_pass(self):
pass

}}}
--

Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:2>

Django

unread,

Jul 4, 2025, 11:56:10 AMJul 4

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Owner: (none)
Soriano Marmol |
Type: Bug | Status: new
Component: Testing framework | Version: 5.2
Severity: Normal | Resolution:

Keywords: tests, parallel, | Triage Stage: Accepted
buffer |

Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Simon Charette):

* stage: Unreviewed => Accepted

Comment:

Managed to reproduce by using `unitest.TestCase` as well

{{{#!python
from unittest import TestCase

class AbortingTest(TestCase):
@classmethod
def setUpClass(cls):
raise RuntimeError("Boo!")

def test_pass(self):
pass

class AbortingTest2(TestCase):

@classmethod
def setUpClass(cls):
raise RuntimeError("Boo!")

def test_pass(self):
pas
}}}

the problem seems due to the fact that the normal `unittest`
[https://github.com/python/cpython/blob/ade19880943509945da193202ca89e0b2b6fbd75/Lib/unittest/suite.py#L162-L186
suite setup makes sure to] call `TestResutl._setupStdout`
[https://github.com/python/cpython/blob/ade19880943509945da193202ca89e0b2b6fbd75/Lib/unittest/result.py#L65-L71
method] prior to calling `setUpClass` which allows its `addError`
[https://github.com/python/cpython/blob/ade19880943509945da193202ca89e0b2b6fbd75/Lib/unittest/suite.py#L238-L253
handler] to not crash when it takes its `if self.buffer`
[https://github.com/python/cpython/blob/ade19880943509945da193202ca89e0b2b6fbd75/Lib/unittest/result.py#L197-L207
branch] in `_exc_info_to_string.

Given the buffering should happened in spawned worker process and we
basically only use the `TestResult` provided to `ParallelTestSuite.run`
for replicating the events sent from the pool in the main process and
there's no test output to capture on the main process (no tests are run in
the main process) a potential solution could be to simply disable `buffer`
on the accumulator test result.

{{{#!diff
diff --git a/django/test/runner.py b/django/test/runner.py
index 3e5c319ade..a44180b3b6 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -561,6 +561,11 @@ def run(self, result):
]
test_results = pool.imap_unordered(self.run_subsuite.__func__,
args)

+ # Disable buffering on the local test result that will accumulate
+ # remote suites results as each process will take care of its own
+ # buffering and there's nothing to capture on the main process.
+ result.buffer = False
+
while True:
if result.shouldStop:
pool.terminate()
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:3>

Django

unread,

Jul 4, 2025, 12:01:26 PMJul 4

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Owner: (none)
Soriano Marmol |
Type: Bug | Status: new
Component: Testing framework | Version: 5.2
Severity: Normal | Resolution:
Keywords: tests, parallel, | Triage Stage: Accepted
buffer |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):

* cc: Adam Johnson (added)

Comment:

Adam, adding you as you worked on adding `--buffer` support for parallel
tests in #31370.
--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:4>

Django

unread,

Sep 11, 2025, 5:53:08 PMSep 11

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------

Reporter: Rafael Carlos | Owner: Shubham
Soriano Marmol | Akhilesh Singh
Type: Bug | Status: assigned

Changes (by Shubham Akhilesh Singh):

* owner: (none) => Shubham Akhilesh Singh
* status: new => assigned

--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:5>

Django

unread,

Sep 12, 2025, 3:34:28 PM (14 days ago) Sep 12

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Owner: Shubham
Soriano Marmol | Akhilesh Singh
Type: Bug | Status: assigned
Component: Testing framework | Version: 5.2
Severity: Normal | Resolution:
Keywords: tests, parallel, | Triage Stage: Accepted
buffer |

Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Shubham Akhilesh Singh):

* has_patch: 0 => 1

Comment:

Fix PR https://github.com/django/django/pull/19853
--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:6>

Django

unread,

Sep 17, 2025, 8:44:12 AM (9 days ago) Sep 17

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Owner: Shubham
Soriano Marmol | Akhilesh Singh
Type: Bug | Status: assigned
Component: Testing framework | Version: 5.2
Severity: Normal | Resolution:
Keywords: tests, parallel, | Triage Stage: Accepted
buffer |
Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 1

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Adam Johnson):

* needs_better_patch: 0 => 1

--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:7>

Django

unread,

Sep 25, 2025, 2:00:09 PM (20 hours ago) Sep 25

to django-...@googlegroups.com

#36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when
setUpTestData raises and tests are run with –parallel –buffer
-------------------------------------+-------------------------------------
Reporter: Rafael Carlos | Owner: Shubham
Soriano Marmol | Akhilesh Singh
Type: Bug | Status: assigned
Component: Testing framework | Version: 5.2
Severity: Normal | Resolution:

Keywords: tests, parallel, | Triage Stage: Ready for
buffer | checkin

Has patch: 1 | Needs documentation: 0

Needs tests: 0 | Patch needs improvement: 0

Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Jacob Walls):

* needs_better_patch: 1 => 0
* stage: Accepted => Ready for checkin

--
Ticket URL: <https://code.djangoproject.com/ticket/36491#comment:8>

Reply all

Reply to author

Forward

[Django] #36491: AttributeError: '_io.TextIOWrapper' object has no attribute 'getvalue' when setUpTestData raises and tests are run with –parallel–buffer

Django

Django

Django

Django

Django

Django

Django

Django

Django

Django

Django