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Update flaky.rst

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Bruno Oliveira 2024-05-24 08:03:03 -03:00 committed by GitHub
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doc/en/explanation/flaky.rst
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@ -30,22 +30,22 @@ Overly strict assertion
Overly strict assertions can cause problems with floating point comparison as well as timing issues. :func:`pytest.approx` is useful here.
pytest thread safety
~~~~~~~~~~~~~~~~~~~~
Thread safety
~~~~~~~~~~~~~
pytest is single-threaded, executing its tests always in the same thread, sequentially, never spawning any threads itself.
Even in case of plugins which run tests in parallel, for example `pytest-xdist`_, usually work by spawns multiple *processes* and running tests in batches, without using threads.
Even in case of plugins which run tests in parallel, for example `pytest-xdist`_, usually work by spawning multiple *processes* and running tests in batches, without using multiple threads.
It is of course possible (and common) for tests and fixtures to spawn threads themselves as part of their testing workflow (for example, a fixture that starts a server thread in the background, or a test which executes production code which itself spawns threads), but some care must be taken:
It is of course possible (and common) for tests and fixtures to spawn threads themselves as part of their testing workflow (for example, a fixture that starts a server thread in the background, or a test which executes production code that spawns threads), but some care must be taken:
* Make sure to eventually wait on any spawned threads -- for example at the end of a test, or during teardown of a fixture.
* Make sure to eventually wait on any spawned threads -- for example at the end of a test, or during the teardown of a fixture.
* Avoid using primitives provided by pytest (:func:`pytest.warns`, :func:`pytest.raises`, etc) from multiple threads, as they are not thread-safe.
If your test suite uses threads and your are seeing flaky test results, do not discount the possibility that the test is implicitly using global state in pytest itself.
Pytest features
^^^^^^^^^^^^^^^
Related features
^^^^^^^^^^^^^^^^
Xfail strict
~~~~~~~~~~~~
@ -136,3 +136,6 @@ Resources
* `Flaky Tests at Google and How We Mitigate Them <https://testing.googleblog.com/2016/05/flaky-tests-at-google-and-how-we.html>`_ by John Micco, 2016
* `Where do Google's flaky tests come from? <https://testing.googleblog.com/2017/04/where-do-our-flaky-tests-come-from.html>`_ by Jeff Listfield, 2017
.. _pytest-xdist: https://github.com/pytest-dev/pytest-xdist