pytest testing fails with `-x`

[mtelka]

When I run tests with the -x pytest option then I see this failure:

============================= test session starts ==============================
platform sunos5 -- Python 3.9.19, pytest-8.3.1, pluggy-1.5.0 -- /usr/bin/python3.9
cachedir: .pytest_cache
rootdir: /data/builds/oi-userland/components/python/pytest-system-statistics/build/amd64-3.9
configfile: pytest.ini
testpaths: tests/
plugins: skip-markers-1.5.1, system-statistics-1.0.2
collecting ... collected 7 items
            
tests/functional/test_syststats.py::test_sys_stats_not_verbose PASSED    [ 14%]
tests/functional/test_syststats.py::test_sys_stats_not_verbose_enough PASSED [ 28%]
tests/functional/test_syststats.py::test_sys_stats_disabled PASSED       [ 42%]
tests/functional/test_syststats.py::test_basic_sys_stats PASSED          [ 57%]
tests/functional/test_syststats.py::test_basic_sys_stats_uss SKIPPED     [ 71%]
tests/functional/test_syststats.py::test_proc_sys_stats FAILED           [ 85%]
    
=================================== FAILURES ===================================
_____________________________ test_proc_sys_stats ______________________________

pytester = <Pytester PosixPath('/tmp/pytest-of-marcel/pytest-12/test_proc_sys_stats0')>
tmp_path = PosixPath('/tmp/pytest-of-marcel/pytest-12/test_proc_sys_stats1')
                
    def test_proc_sys_stats(pytester, tmp_path):
        executable = sys.executable
        script1 = tmp_path / "script1.py"
        script1.write_text(
            textwrap.dedent(
                """\
            import time
            import multiprocessing
 
            if __name__ == '__main__':
                multiprocessing.freeze_support()
                try:
                    while True:
                        time.sleep(0.25)
                except Exception:
                    pass
            """
            )
        )
        script2 = tmp_path / "script2.py"
        script2.write_text(
            textwrap.dedent(
                """\      
            import sys
            import subprocess
            import multiprocessing
          
            if __name__ == '__main__':
                multiprocessing.freeze_support()
                proc = subprocess.run([r"{}", r"{}"])
            """.format(
                    executable, script1
                )
            )
        )
        pytester.makepyfile(
            """
            import sys
            import pytest 
            import subprocess
            import psutil
            import time
    
            @pytest.fixture
            def foo_process(stats_processes):
                proc = subprocess.Popen([r"{}", r"{}"])
                try:
                    time.sleep(0.25)
                    assert psutil.Process(proc.pid).children()
                    stats_processes.add("FooProcess", proc.pid)
                    yield proc
                finally:
                    stats_processes.remove("FooProcess")
                    proc.terminate()

            def test_one(foo_process):
                assert True
            """.format(
                executable, script2
            )
        )
        res = pytester.runpytest("-vv", "--sys-stats")
>       res.assert_outcomes(passed=1)
E       AssertionError: assert {'passed': 0, 'skipped': 0, 'failed': 0, 'errors': 1, 'xpassed': 0, 'xfailed': 0} == {'passed': 1, 'skipped': 0, 'failed': 0, 'errors': 0, 'xpassed': 0, 'xfailed': 0}
E
E         Common items:
E         {'failed': 0, 'skipped': 0, 'xfailed': 0, 'xpassed': 0}
E         Differing items:
E         {'passed': 0} != {'passed': 1}
E         {'errors': 1} != {'errors': 0}
E
E         Full diff:
E           {
E         -     'errors': 0,
E         ?               ^
E         +     'errors': 1,
E         ?               ^
E               'failed': 0,
E         -     'passed': 1,
E         ?               ^
E         +     'passed': 0,
E         ?               ^
E               'skipped': 0,
E               'xfailed': 0,
E               'xpassed': 0,
E           }

/data/builds/oi-userland/components/python/pytest-system-statistics/build/amd64-3.9/tests/functional/test_syststats.py:182: AssertionError
----------------------------- Captured stdout call -----------------------------
============================= test session starts ==============================
platform sunos5 -- Python 3.9.19, pytest-8.3.1, pluggy-1.5.0 -- /usr/bin/python3.9
cachedir: .pytest_cache
rootdir: /tmp/pytest-of-marcel/pytest-12/test_proc_sys_stats0
plugins: skip-markers-1.5.1, system-statistics-1.0.2
collecting ... collected 1 item

test_proc_sys_stats.py::test_one ERROR                                   [100%]

==================================== ERRORS ====================================
__________________________ ERROR at setup of test_one __________________________

stats_processes = StatsProcesses(processes=OrderedDict([('Test Suite Run', psutil.Process(pid=2917, name='python3.9', status='running', started='11:59:06'))]))

    @pytest.fixture
    def foo_process(stats_processes):
        proc = subprocess.Popen([r"/usr/bin/python3.9", r"/tmp/pytest-of-marcel/pytest-12/test_proc_sys_stats1/script2.py"])
        try:
            time.sleep(0.25)
>           assert psutil.Process(proc.pid).children()
E           AssertionError: assert []
E            +  where [] = children()
E            +    where children = psutil.Process(pid=2923, name='python3.9', status='running', started='11:59:10').children
E            +      where psutil.Process(pid=2923, name='python3.9', status='running', started='11:59:10') = <class 'psutil.Process'>(2923)
E            +        where <class 'psutil.Process'> = psutil.Process
E            +        and   2923 = <Popen: returncode: None args: ['/usr/bin/python3.9', '/tmp/pytest-of-marcel...>.pid

test_proc_sys_stats.py:12: AssertionError
=========================== short test summary info ============================
ERROR test_proc_sys_stats.py::test_one - AssertionError: assert []
 +  where [] = children()
 +    where children = psutil.Process(pid=2923, name='python3.9', status='running', started='11:59:10').children
 +      where psutil.Process(pid=2923, name='python3.9', status='running', started='11:59:10') = <class 'psutil.Process'>(2923)
 +        where <class 'psutil.Process'> = psutil.Process
 +        and   2923 = <Popen: returncode: None args: ['/usr/bin/python3.9', '/tmp/pytest-of-marcel...>.pid
=============================== 1 error in 0.36s ===============================
=========================== short test summary info ============================
FAILED tests/functional/test_syststats.py::test_proc_sys_stats - AssertionError: assert {'passed': 0, 'skipped': 0, 'failed': 0, 'errors': 1, 'xpassed': 0, 'xfailed': 0} == {'passed': 1, 'skipped': 0, 'failed': 0, 'errors': 0, 'xpassed': 0, 'xfailed': 0}

  Common items:
  {'failed': 0, 'skipped': 0, 'xfailed': 0, 'xpassed': 0}
  Differing items:
  {'passed': 0} != {'passed': 1}
  {'errors': 1} != {'errors': 0}

  Full diff:
    {
  -     'errors': 0,
  ?               ^
  +     'errors': 1,
  ?               ^
        'failed': 0,
  -     'passed': 1,
  ?               ^
  +     'passed': 0,
  ?               ^
        'skipped': 0,
        'xfailed': 0,
        'xpassed': 0,
    }
!!!!!!!!!!!!!!!!!!!!!!!!!! stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!
==================== 1 failed, 4 passed, 1 skipped in 2.50s ====================

When I do not use -x then all tests pass:

============================= test session starts ==============================
platform sunos5 -- Python 3.9.19, pytest-8.3.1, pluggy-1.5.0 -- /usr/bin/python3.9
cachedir: .pytest_cache
rootdir: /data/builds/oi-userland/components/python/pytest-system-statistics/build/amd64-3.9
configfile: pytest.ini
testpaths: tests/
plugins: skip-markers-1.5.1, system-statistics-1.0.2
collecting ... collected 7 items

tests/functional/test_syststats.py::test_sys_stats_not_verbose PASSED    [ 14%]
tests/functional/test_syststats.py::test_sys_stats_not_verbose_enough PASSED [ 28%]
tests/functional/test_syststats.py::test_sys_stats_disabled PASSED       [ 42%]
tests/functional/test_syststats.py::test_basic_sys_stats PASSED          [ 57%]
tests/functional/test_syststats.py::test_basic_sys_stats_uss SKIPPED     [ 71%]
tests/functional/test_syststats.py::test_proc_sys_stats PASSED           [ 85%]
tests/functional/test_syststats.py::test_proc_sys_stats_no_children PASSED [100%]

========================= 6 passed, 1 skipped in 1.76s =========================