pytest-timeout 2.3.1

Description:

pytesttimeout 2.3.1

Warning
Please read this README carefully and only use this plugin if you
understand the consequences. This plugin is designed to catch
excessively long test durations like deadlocked or hanging tests,
it is not designed for precise timings or performance regressions.
Remember your test suite should aim to be fast, with timeouts
being a last resort, not an expected failure mode.

This plugin will time each test and terminate it when it takes too
long. Termination may or may not be graceful, please see below, but
when aborting it will show a stack dump of all thread running at the
time. This is useful when running tests under a continuous
integration server or simply if you don’t know why the test suite
hangs.

Note
While by default on POSIX systems pytest will continue to execute
the tests after a test has timed out this is not always possible.
Often the only sure way to interrupt a hanging test is by
terminating the entire process. As this is a hard termination
(os._exit()) it will result in no teardown, JUnit XML output
etc. But the plugin will ensure you will have the debugging output
on stderr nevertheless, which is the most important part at this
stage. See below for detailed information on the timeout methods
and their side-effects.

The pytest-timeout plugin has been tested on Python 3.6 and higher,
including PyPy3. See tox.ini for currently tested versions.

Usage
Install is as simple as e.g.:
pip install pytest-timeout
Now you can run the test suite while setting a timeout in seconds, any
individual test which takes longer than the given duration will be
terminated:
pytest --timeout=300
Furthermore you can also use a decorator to set the timeout for an
individual test. If combined with the --timeout flag this will
override the timeout for this individual test:
@pytest.mark.timeout(60)
def test_foo():
pass
By default the plugin will not time out any tests, you must specify a
valid timeout for the plugin to interrupt long-running tests. A
timeout is always specified as a number of seconds, and can be
defined in a number of ways, from low to high priority:

You can set a global timeout in the pytest configuration file
using the timeout option. E.g.:
[pytest]
timeout = 300

The PYTEST_TIMEOUT environment variable sets a global timeout
overriding a possible value in the configuration file.
The --timeout command line option sets a global timeout
overriding both the environment variable and configuration option.
Using the timeout marker on test items you can specify
timeouts on a per-item basis:
@pytest.mark.timeout(300)
def test_foo():
pass


Setting a timeout to 0 seconds disables the timeout, so if you have a
global timeout set you can still disable the timeout by using the
mark.


Timeout Methods
Interrupting tests which hang is not always as simple and can be
platform dependent. Furthermore some methods of terminating a test
might conflict with the code under test itself. The pytest-timeout
plugin tries to pick the most suitable method based on your platform,
but occasionally you may need to specify a specific timeout method
explicitly.

If a timeout method does not work your safest bet is to use the
thread method.


thread
This is the surest and most portable method. It is also the default
on systems not supporting the signal method. For each test item the
pytest-timeout plugin starts a timer thread which will terminate the
whole process after the specified timeout. When a test item finishes
this timer thread is cancelled and the test run continues.
The downsides of this method are that there is a relatively large
overhead for running each test and that test runs are not completed.
This means that other pytest features, like e.g. JUnit XML output or
fixture teardown, will not function normally. The second issue might
be alleviated by using the --boxed option of the pytest-xdist
plugin.
The benefit of this method is that it will always work. Furthermore
it will still provide you debugging information by printing the stacks
of all the threads in the application to stderr.


signal
If the system supports the SIGALRM signal the signal method will be
used by default. This method schedules an alarm when the test item
starts and cancels the alarm when the test finishes. If the alarm expires
during the test the signal handler will dump the stack of any other threads
running to stderr and use pytest.fail() to interrupt the test.
The benefit of this method is that the pytest process is not
terminated and the test run can complete normally.
The main issue to look out for with this method is that it may
interfere with the code under test. If the code under test uses
SIGALRM itself things will go wrong and you will have to choose the
thread method.


Specifying the Timeout Method
The timeout method can be specified by using the timeout_method
option in the pytest configuration file, the --timeout_method
command line parameter or the timeout marker. Simply set their
value to the string thread or signal to override the default
method. On a marker this is done using the method keyword:
@pytest.mark.timeout(method="thread")
def test_foo():
pass



The timeout Marker API
The full signature of the timeout marker is:
pytest.mark.timeout(timeout=0, method=DEFAULT_METHOD)
You can use either positional or keyword arguments for both the
timeout and the method. Neither needs to be present.
See the marker api documentation and examples for the various ways
markers can be applied to test items.


Timeouts in Fixture Teardown
The plugin will happily terminate timeouts in the finalisers of
fixtures. The timeout specified applies to the entire process of
setting up fixtures, running the tests and finalising the fixtures.
However when a timeout occurs in a fixture finaliser and the test
suite continues, i.e. the signal method is used, it must be realised
that subsequent fixtures which need to be finalised might not have
been executed, which could result in a broken test-suite anyway. In
case of doubt the thread method which terminates the entire process
might result in clearer output.


Avoiding timeouts in Fixtures
The timeout applies to the entire test including any fixtures which
may need to be setup or torn down for the test (the exact affected
fixtures depends on which scope they are and whether other tests will
still use the same fixture). If the timeouts really are too short to
include fixture durations, firstly make the timeouts larger ;). If
this really isn’t an option a timeout_func_only boolean setting
exists which can be set in the pytest ini configuration file, as
documented in pytest --help.
For the decorated function, a decorator will override
timeout_func_only = true in the pytest ini file to the default
value. If you need to keep this option for a decorated test, you
must specify the option explicitly again:
@pytest.mark.timeout(60, func_only=True)
def test_foo():
pass


Debugger Detection
This plugin tries to avoid triggering the timeout when a debugger is
detected. This is mostly a convenience so you do not need to remember
to disable the timeout when interactively debugging.
The way this plugin detects whether or not a debugging session is
active is by checking if a trace function is set and if one is, it
check to see if the module it belongs to is present in a set of known
debugging frameworks modules OR if pytest itself drops you into a pdb
session using --pdb or similar.
This functionality can be disabled with the --disable-debugger-detection flag
or the corresponding timeout_disable_debugger_detection ini setting / environment
variable.


Extending pytest-timeout with plugins
pytest-timeout provides two hooks that can be used for extending the tool. These
hooks are used for setting the timeout timer and cancelling it if the timeout is not
reached.
For example, pytest-asyncio can provide asyncio-specific code that generates better
traceback and points on timed out await instead of the running loop iteration.
See pytest hooks documentation for more info
regarding to use custom hooks.

pytest_timeout_set_timer
@pytest.hookspec(firstresult=True)
def pytest_timeout_set_timer(item, settings):
"""Called at timeout setup.

'item' is a pytest node to setup timeout for.

'settings' is Settings namedtuple (described below).

Can be overridden by plugins for alternative timeout implementation strategies.
"""


Settings
When pytest_timeout_set_timer is called, settings argument is passed.
The argument has Settings namedtuple type with the following fields:


Attribute
Index
Value



timeout
0
timeout in seconds or None for no timeout

method
1
Method mechanism,
'signal' and 'thread' are supported by default

func_only
2

Apply timeout to test function only if True,
wrap all test function and its fixtures otherwise








pytest_timeout_cancel_timer
@pytest.hookspec(firstresult=True)
def pytest_timeout_cancel_timer(item):
"""Called at timeout teardown.

'item' is a pytest node which was used for timeout setup.

Can be overridden by plugins for alternative timeout implementation strategies.
"""


is_debugging
When the timeout occurs, user can open the debugger session. In this case, the timeout
should be discarded. A custom hook can check this case by calling is_debugging()
function:
import pytest
import pytest_timeout


def on_timeout():
if pytest_timeout.is_debugging():
return
pytest.fail("+++ Timeout +++")



Session Timeout
The above mentioned timeouts are all per test function.
The “per test function” timeouts will stop an individual test
from taking too long. We may also want to limit the time of the entire
set of tests running in one session. A session all of the tests
that will be run with one invokation of pytest.
A session timeout is set with –session-timeout and is in seconds.
The following example shows a session timeout of 10 minutes (600 seconds):
pytest --session-timeout=600
You can also set the session timeout the pytest configuration file using the session_timeout option:

[pytest]
session_timeout = 600


Cooperative timeouts
Session timeouts are cooperative timeouts. pytest-timeout checks the
session time at the end of each test function, and stops further tests
from running if the session timeout is exceeded. The session will
results in a test failure if this occurs.
In particular this means if a test does not finish of itself, it will
only be interrupted if there is also a function timeout set. A
session timeout is not enough to ensure that a test-suite is
guaranteed to finish.


Combining session and function timeouts
It works fine to combine both session and function timeouts. In fact
when using a session timeout it is recommended to also provide a
function timeout.
For example, to limit test functions to 5 seconds and the full session
to 100 seconds:
pytest --timeout=5 --session-timeout=100



Changelog

2.3.1

Fixup some build errors, mostly README syntax which stopped twine
from uploading.



2.3.0

Fix debugger detection for recent VSCode, this compiles pydevd using
cython which is now correctly detected. Thanks Adrian Gielniewski.
Switched to using Pytest’s TerminalReporter instead of writing
directly to sys.{stdout,stderr}.
This change also switches all output from sys.stderr to sys.stdout.
Thanks Pedro Algarvio.
Pytest 7.0.0 is now the minimum supported version. Thanks Pedro Algarvio.
Add --session-timeout option and session_timeout setting.
Thanks Brian Okken.



2.2.0

Add --timeout-disable-debugger-detection flag, thanks
Michael Peters



2.1.0

Get terminal width from shutil instead of deprecated py, thanks
Andrew Svetlov.
Add an API for extending pytest-timeout functionality
with third-party plugins, thanks Andrew Svetlov.



2.0.2

Fix debugger detection on OSX, thanks Alexander Pacha.



2.0.1

Fix Python 2 removal, thanks Nicusor Picatureanu.



2.0.0

Increase pytest requirement to >=5.0.0. Thanks Dominic Davis-Foster.
Use thread timeout method when plugin is not called from main
thread to avoid crash.
Fix pycharm debugger detection so timeouts are not triggered during
debugger usage.
Dropped support for Python 2, minimum pytest version supported is 5.0.0.



1.4.2

Fix compatibility when run with pytest pre-releases, thanks
Bruno Oliveira,
Fix detection of third-party debuggers, thanks Bruno Oliveira.



1.4.1

Fix coverage compatibility which was broken by 1.4.0.



1.4.0

Better detection of when we are debugging, thanks Mattwmaster58.



1.3.4

Give the threads a name to help debugging, thanks Thomas Grainger.
Changed location to https://github.com/pytest-dev/pytest-timeout
because bitbucket is dropping mercurial support. Thanks Thomas
Grainger and Bruno Oliveira.



1.3.3

Fix support for pytest >= 3.10.



1.3.2

This changelog was omitted for the 1.3.2 release and was added
afterwards. Apologies for the confusion.
Fix pytest 3.7.3 compatibility. The capture API had changed
slightly and this needed fixing. Thanks Bruno Oliveira for the
contribution.



1.3.1

Fix deprecation warning on Python 3.6. Thanks Mickaël Schoentgen
Create a valid tag for the release. Somehow this didn’t happen for
1.3.0, that tag points to a non-existing commit.



1.3.0

Make it possible to only run the timeout timer on the test function
and not the whole fixture setup + test + teardown duration. Thanks
Pedro Algarvio for the work!
Use the new pytest marker API, Thanks Pedro Algarvio for the work!



1.2.1

Fix for pytest 3.3, thanks Bruno Oliveira.
Update supported python versions:
- Add CPython 3.6.
- Drop CPyhon 2.6 (as did pytest 3.3)
- Drop CPyhon 3.3
- Drop CPyhon 3.4



1.2.0

Allow using floats as timeout instead of only integers, thanks Tom
Myers.



1.1.0

Report (default) timeout duration in header, thanks Holger Krekel.



1.0.0

Bump version to 1.0 to commit to semantic versioning.
Fix issue #12: Now compatible with pytest 2.8, thanks Holger Krekel.
No longer test with pexpect on py26 as it is no longer supported
Require pytest 2.8 and use new hookimpl decorator



0.5

Timeouts will no longer be triggered when inside an interactive pdb
session started by pytest.set_trace() / pdb.set_trace().
Add pypy3 environment to tox.ini.
Transfer repository to pytest-dev team account.



0.4

Support timeouts happening in (session scoped) finalizers.
Change command line option –timeout_method into –timeout-method
for consistency with pytest



0.3

Added the PYTEST_TIMEOUT environment variable as a way of specifying
the timeout (closes issue #2).
More flexible marker argument parsing: you can now specify the
method using a positional argument.
The plugin is now enabled by default. There is no longer a need to
specify timeout=0 in the configuration file or on the command
line simply so that a marker would work.



0.2

Add a marker to modify the timeout delay using a @pytest.timeout(N)
syntax, thanks to Laurant Brack for the initial code.
Allow the timeout marker to select the timeout method using the
method keyword argument.
Rename the –nosigalrm option to –method=thread to future proof
support for eventlet and gevent. Thanks to Ronny Pfannschmidt for
the hint.
Add timeout and timeout_method items to the configuration
file so you can enable and configure the plugin using the ini file.
Thanks to Holger Krekel and Ronny Pfannschmidt for the hints.
Tested (and fixed) for python 2.6, 2.7 and 3.2.