273 lines
7.1 KiB
ReStructuredText
273 lines
7.1 KiB
ReStructuredText
Cache: working with cross-testrun state
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=======================================
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.. versionadded:: 2.8
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.. warning::
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The functionality of this core plugin was previously distributed
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as a third party plugin named ``pytest-cache``. The core plugin
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is compatible regarding command line options and API usage except that you
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can only store/receive data between test runs that is json-serializable.
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Usage
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---------
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The plugin provides two command line options to rerun failures from the
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last ``pytest`` invocation:
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* ``--lf``, ``--last-failed`` - to only re-run the failures.
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* ``--ff``, ``--failed-first`` - to run the failures first and then the rest of
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the tests.
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For cleanup (usually not needed), a ``--cache-clear`` option allows to remove
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all cross-session cache contents ahead of a test run.
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Other plugins may access the `config.cache`_ object to set/get
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**json encodable** values between ``pytest`` invocations.
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.. note::
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This plugin is enabled by default, but can be disabled if needed: see
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:ref:`cmdunregister` (the internal name for this plugin is
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``cacheprovider``).
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Rerunning only failures or failures first
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-----------------------------------------------
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First, let's create 50 test invocation of which only 2 fail::
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# content of test_50.py
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import pytest
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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pytest.fail("bad luck")
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If you run this for the first time you will see two failures::
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$ pytest -q
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.................F.......F........................
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======= FAILURES ========
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_______ test_num[17] ________
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i = 17
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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> pytest.fail("bad luck")
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E Failed: bad luck
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test_50.py:6: Failed
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_______ test_num[25] ________
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i = 25
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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> pytest.fail("bad luck")
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E Failed: bad luck
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test_50.py:6: Failed
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2 failed, 48 passed in 0.12 seconds
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If you then run it with ``--lf``::
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$ pytest --lf
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======= test session starts ========
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platform linux -- Python 3.5.2, pytest-3.0.0, py-1.4.31, pluggy-0.3.1
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run-last-failure: rerun last 2 failures
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rootdir: $REGENDOC_TMPDIR, inifile:
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collected 50 items
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test_50.py FF
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======= FAILURES ========
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_______ test_num[17] ________
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i = 17
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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> pytest.fail("bad luck")
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E Failed: bad luck
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test_50.py:6: Failed
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_______ test_num[25] ________
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i = 25
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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> pytest.fail("bad luck")
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E Failed: bad luck
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test_50.py:6: Failed
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======= 48 tests deselected ========
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======= 2 failed, 48 deselected in 0.12 seconds ========
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You have run only the two failing test from the last run, while 48 tests have
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not been run ("deselected").
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Now, if you run with the ``--ff`` option, all tests will be run but the first
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previous failures will be executed first (as can be seen from the series
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of ``FF`` and dots)::
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$ pytest --ff
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======= test session starts ========
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platform linux -- Python 3.5.2, pytest-3.0.0, py-1.4.31, pluggy-0.3.1
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run-last-failure: rerun last 2 failures first
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rootdir: $REGENDOC_TMPDIR, inifile:
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collected 50 items
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test_50.py FF................................................
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======= FAILURES ========
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_______ test_num[17] ________
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i = 17
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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> pytest.fail("bad luck")
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E Failed: bad luck
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test_50.py:6: Failed
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_______ test_num[25] ________
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i = 25
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@pytest.mark.parametrize("i", range(50))
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def test_num(i):
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if i in (17, 25):
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> pytest.fail("bad luck")
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E Failed: bad luck
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test_50.py:6: Failed
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======= 2 failed, 48 passed in 0.12 seconds ========
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.. _`config.cache`:
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The new config.cache object
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--------------------------------
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.. regendoc:wipe
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Plugins or conftest.py support code can get a cached value using the
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pytest ``config`` object. Here is a basic example plugin which
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implements a :ref:`fixture` which re-uses previously created state
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across pytest invocations::
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# content of test_caching.py
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import pytest
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import time
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@pytest.fixture
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def mydata(request):
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val = request.config.cache.get("example/value", None)
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if val is None:
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time.sleep(9*0.6) # expensive computation :)
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val = 42
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request.config.cache.set("example/value", val)
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return val
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def test_function(mydata):
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assert mydata == 23
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If you run this command once, it will take a while because
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of the sleep::
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$ pytest -q
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F
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======= FAILURES ========
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_______ test_function ________
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mydata = 42
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def test_function(mydata):
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> assert mydata == 23
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E assert 42 == 23
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test_caching.py:14: AssertionError
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1 failed in 0.12 seconds
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If you run it a second time the value will be retrieved from
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the cache and this will be quick::
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$ pytest -q
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F
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======= FAILURES ========
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_______ test_function ________
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mydata = 42
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def test_function(mydata):
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> assert mydata == 23
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E assert 42 == 23
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test_caching.py:14: AssertionError
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1 failed in 0.12 seconds
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See the `cache-api`_ for more details.
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Inspecting Cache content
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-------------------------------
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You can always peek at the content of the cache using the
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``--cache-show`` command line option::
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$ py.test --cache-show
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======= test session starts ========
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platform linux -- Python 3.5.2, pytest-3.0.0, py-1.4.31, pluggy-0.3.1
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rootdir: $REGENDOC_TMPDIR, inifile:
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cachedir: $REGENDOC_TMPDIR/.cache
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------------------------------- cache values -------------------------------
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cache/lastfailed contains:
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{'test_caching.py::test_function': True}
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example/value contains:
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42
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======= no tests ran in 0.12 seconds ========
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Clearing Cache content
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-------------------------------
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You can instruct pytest to clear all cache files and values
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by adding the ``--cache-clear`` option like this::
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pytest --cache-clear
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This is recommended for invocations from Continous Integration
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servers where isolation and correctness is more important
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than speed.
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.. _`cache-api`:
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config.cache API
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------------------
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The ``config.cache`` object allows other plugins,
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including ``conftest.py`` files,
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to safely and flexibly store and retrieve values across
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test runs because the ``config`` object is available
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in many places.
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Under the hood, the cache plugin uses the simple
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dumps/loads API of the json stdlib module
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.. currentmodule:: _pytest.cacheprovider
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.. automethod:: Cache.get
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.. automethod:: Cache.set
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.. automethod:: Cache.makedir
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