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[7.1.x] Update fixtures.rst w/ finalizer order
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aizpurua23a authored and pytestbot committed Aug 15, 2022
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77 changes: 75 additions & 2 deletions doc/en/how-to/fixtures.rst
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Expand Up @@ -733,8 +733,81 @@ does offer some nuances for when you're in a pinch.
.. code-block:: pytest
$ pytest -q test_emaillib.py
. [100%]
1 passed in 0.12s
. [100%]
1 passed in 0.12s
Note on finalizer order
""""""""""""""""""""""""

Finalizers are executed in a first-in-last-out order.
For yield fixtures, the first teardown code to run is from the right-most fixture, i.e. the last test parameter.

.. regendoc:wipe
.. code-block:: python
import pytest
def test_bar(fix_w_yield1, fix_w_yield2):
print("test_bar")
@pytest.fixture
def fix_w_yield1():
yield
print("after_yield_1")
@pytest.fixture
def fix_w_yield2():
yield
print("after_yield_2")
.. code-block:: pytest
$ pytest test_module.py
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-7.x.y, pluggy-1.x.y
collected 1 item
test_module.py test_bar
.after_yield_2
after_yield_1
For finalizers, the first fixture to run is last call to `request.addfinalizer`.

.. code-block:: python
import pytest
@pytest.fixture
def fix_w_finalizers(request):
request.addfinalizer(partial(print, "finalizer_2"))
request.addfinalizer(partial(print, "finalizer_1"))
def test_bar(fix_w_finalizers):
print("test_bar")
.. code-block:: pytest
$ pytest test_module.py
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-7.x.y, pluggy-1.x.y
collected 1 item
test_module.py test_bar
.finalizer_1
finalizer_2
This is so because yield fixtures use `addfinalizer` behind the scenes: when the fixture executes, `addfinalizer` registers a function that resumes the generator, which in turn calls the teardown code.


.. _`safe teardowns`:

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