pytester (?) causes monkeypatch to not tear down correctly #9708
Description
have a difficult time tracking down the "why" for this but I've narrowed it down to this minimal testcase:
import os
import pytest
def test_a(monkeypatch, pytester): # removing `pytester` here causes the session fixture to "pass"
monkeypatch.setenv("PY_COLORS", "1")
@pytest.fixture(autouse=True, scope='session')
def t():
yield
assert 'PY_COLORS' not in os.environ$ pytest -p pytester t.py
============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-7.1.0.dev230+g3b549642e, pluggy-1.0.0
rootdir: /tmp/pytest, configfile: pyproject.toml
plugins: hypothesis-6.37.2
collected 1 item
t.py .E [100%]
==================================== ERRORS ====================================
_________________________ ERROR at teardown of test_a __________________________
@pytest.fixture(autouse=True, scope='session')
def t():
yield
> assert 'PY_COLORS' not in os.environ
E AssertionError: assert 'PY_COLORS' not in environ({'SHELL': '/bin/bash', 'SESSION_MANAGER': 'local/babibox:@/tmp/.ICE-unix/1733,unix/babibox:/tmp/.ICE-unix/1733...st-pollution', '_': '/tmp/pytest/venv/bin/pytest', 'PYTEST_CURRENT_TEST': 't.py::test_a (teardown)', 'PY_COLORS': '0'})
E + where environ({'SHELL': '/bin/bash', 'SESSION_MANAGER': 'local/babibox:@/tmp/.ICE-unix/1733,unix/babibox:/tmp/.ICE-unix/1733...st-pollution', '_': '/tmp/pytest/venv/bin/pytest', 'PYTEST_CURRENT_TEST': 't.py::test_a (teardown)', 'PY_COLORS': '0'}) = os.environ
t.py:12: AssertionError
=========================== short test summary info ============================
ERROR t.py::test_a - AssertionError: assert 'PY_COLORS' not in environ({'SHEL...
========================== 1 passed, 1 error in 0.18s ==========================in our self tests this can be reproduced if you can run these tests in order (I can't figure out a definitive way to force that using just pytest (pytest seems to want to reorder them even when they're passed in an explicit order on the commandline) -- but my test pollution finder is able to do this, and I suspect pytest-select can too):
testing/test_terminal.py::TestTerminal::test_report_teststatus_explicit_markup
testing/io/test_terminalwriter.py::test_should_do_markup_FORCE_COLOR
$ pytest -s -v -p detect_test_pollution --dtp-testids-input-file /dev/stdin testing <<< $'testing/test_terminal.py::TestTerminal::test_report_teststatus_explicit_markup\ntesting/io/test_terminalwriter.py::test_should_do_markup_FORCE_COLOR'
============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-7.1.0.dev230+g3b549642e, pluggy-1.0.0 -- /tmp/pytest/venv/bin/python
cachedir: .pytest_cache
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('/tmp/pytest/.hypothesis/examples')
rootdir: /tmp/pytest, configfile: pyproject.toml, testpaths: testing
plugins: hypothesis-6.37.2
collected 3140 items
testing/test_terminal.py::TestTerminal::test_report_teststatus_explicit_markup ============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-7.1.0.dev230+g3b549642e, pluggy-1.0.0 -- /tmp/pytest/venv/bin/python
cachedir: .pytest_cache
rootdir: /tmp/pytest-of-asottile/pytest-272/test_report_teststatus_explicit_markup0
collecting ... collected 1 item
test_report_teststatus_explicit_markup.py::test_foobar FOO [100%]
test_report_teststatus_explicit_markup.py::test_foobar FOO [100%]
test_report_teststatus_explicit_markup.py::test_foobar FOO [100%]
================================ 3 foo in 0.00s ================================
PASSED
testing/io/test_terminalwriter.py::test_should_do_markup_FORCE_COLOR FAILED
=================================== FAILURES ===================================
______________________ test_should_do_markup_FORCE_COLOR _______________________
monkeypatch = <_pytest.monkeypatch.MonkeyPatch object at 0x7fae39208520>
def test_should_do_markup_FORCE_COLOR(monkeypatch: MonkeyPatch) -> None:
monkeypatch.setitem(os.environ, "FORCE_COLOR", "1")
> assert_color_set()
testing/io/test_terminalwriter.py:205:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
def assert_color_set():
file = io.StringIO()
tw = terminalwriter.TerminalWriter(file)
> assert tw.hasmarkup
E assert False
E + where False = <_pytest._io.terminalwriter.TerminalWriter object at 0x7fae39199460>.hasmarkup
testing/io/test_terminalwriter.py:170: AssertionError
=========================== short test summary info ============================
FAILED testing/io/test_terminalwriter.py::test_should_do_markup_FORCE_COLOR
========================= 1 failed, 1 passed in 1.42s ==========================