A bunch of CTracer selection (and other) tests fail on Fedora-based dev envs #2050
Description
Describe the bug
So while rebasing #1952, @OlenaYefymenko started seeing an unexpected test failure. It turned out to be a test added in bea6204 — tests/test_process.py::CoverageCoreTest::test_core_request_ctrace_but_missing.
Her dev env is Fedora. It doesn't fail on my Gentoo Linux laptop. So I tried reproducing that in a Fedora container and ended up discovering several things.
- The contributing doc does not explicitly list OS-level prerequisites (gcc, for example) — so a less experienced contributor might be greeted with a wall of errors on the very first tox run. This would be good to improve: [docs] List platform-level prerequisites in the contributing doc #2051.
- There's four tests failing in that env. I haven't checked whether this is due to inadequate test isolation or there's real bugs in there. I think this calls for adding an additional job to the CI running a Fedora container (maybe some more too).
To Reproduce
Here's a one-liner for running what I ran in an F43 container:
$ podman run --rm -it fedora:43 bash -x -c 'dnf install -y gcc git python3.13-freethreading python3.14-freethreading tox && git clone https://github.com/nedbat/coveragepy.git && cd coveragepy && tox'GHA-based repro: #2053 / https://github.com/nedbat/coveragepy/actions/runs/17766812690/job/50492157797?pr=2053#step:7:46.
Expected behavior
All the tests should pass.
Additional context
The entire log is big but here's one of the tox envs that has 4 failing tests (others have fewer failures):
py39: commands[2]> python igor.py test_with_core pytrace
=== CPython 3.9.23 (main Jul 25 2025 00:00:00) (gil) with Python tracer (/usr) ===
bringing up nodes...
.................................................................................................................................................... [ 9%]
...............x....s....s......s.....ss................s.s.......................................s................................................. [ 19%]
.........s..sss.....ss.........s..s................................................................................................................. [ 29%]
.................................................................................................................................................... [ 39%]
.................................................................................................................................................... [ 49%]
......................................................................................................s..........s.................................. [ 58%]
.............................................................................................................ss.s................................... [ 68%]
...................s.....ss.s...........................ss.......................sssss.s..ssssssssss.ssssss........s.......s.........s.............. [ 78%]
.............s.s.s..............s..............s.F..s...................................F........................................................... [ 88%]
................................s............................................................................................s...................... [ 98%]
.......................ss..FF [100%]
========================================================================= FAILURES =========================================================================
____________________________________________________________ CoverageCoreTest.test_core_default ____________________________________________________________
[gw7] linux -- Python 3.9.23 /coveragepy/.tox/py39/bin/python
self = <tests.test_process.CoverageCoreTest object at 0x7f4b4187c880>
def test_core_default(self) -> None:
self.del_environ("COVERAGE_CORE")
self.make_file("numbers.py", "print(123, 456)")
out = self.run_command("coverage run --debug=sys numbers.py")
assert out.endswith("123 456\n")
core = re_line(r" core:", out).strip()
warns = re_lines(r"\(no-ctracer\)", out)
if env.SYSMON_DEFAULT:
assert core == "core: SysMonitor"
assert not warns
elif self.has_ctracer:
assert core == "core: CTracer"
assert not warns
else:
> assert core == "core: PyTracer"
E AssertionError: assert 'core: CTracer' == 'core: PyTracer'
E
E - core: PyTracer
E ? ^^
E + core: CTracer
E ? ^
/coveragepy/tests/test_process.py:1343: AssertionError
------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------
-- sys -------------------------------------------------------
coverage_version: 7.10.7a0.dev1
coverage_module: /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/__init__.py
core: CTracer
CTracer: available from /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/tracer.cpython-39-x86_64-linux-gnu.so
plugins.file_tracers: -none-
plugins.configurers: -none-
plugins.context_switchers: -none-
configs_attempted: /tmp/pytest-of-root/pytest-0/popen-gw7/t23/.coveragerc
/tmp/pytest-of-root/pytest-0/popen-gw7/t23/setup.cfg
/tmp/pytest-of-root/pytest-0/popen-gw7/t23/tox.ini
/tmp/pytest-of-root/pytest-0/popen-gw7/t23/pyproject.toml
configs_read: -none-
config_file: None
config_contents: -none-
data_file: /tmp/pytest-of-root/pytest-0/popen-gw7/t23/.coverage
python: 3.9.23 (main, Jul 25 2025, 00:00:00) [GCC 15.1.1 20250521 (Red Hat 15.1.1-2)]
platform: Linux-6.12.41-gentoo-dist-x86_64-with-glibc2.42
implementation: CPython
build: main
Jul 25 2025 00:00:00
gil_enabled: True
executable: /coveragepy/.tox/py39/bin/python
def_encoding: utf-8
fs_encoding: utf-8
pid: 1641
cwd: /tmp/pytest-of-root/pytest-0/popen-gw7/t23
path: /tmp/pytest-of-root/pytest-0/popen-gw7/t23
/usr/lib64/python39.zip
/usr/lib64/python3.9
/usr/lib64/python3.9/lib-dynload
/coveragepy/.tox/py39/lib64/python3.9/site-packages
/coveragepy/.tox/py39/lib/python3.9/site-packages
environment: COVERAGE_RUN = true
COVERAGE_TESTING = True
HOME = /root
PYTEST_CURRENT_TEST = tests/test_process.py::CoverageCoreTest::test_core_default (call)
PYTEST_VERSION = 8.4.2
PYTEST_XDIST_TESTRUNUID = 096ea5d3b85e456996338b8b35ef51d4
PYTEST_XDIST_WORKER = gw7
PYTEST_XDIST_WORKER_COUNT = 16
PYTHONHASHSEED = 856143455
PYTHONIOENCODING = UTF-8
PYTHONWARNDEFAULTENCODING =
PYTHON_COLORS = 0
command_line: /coveragepy/.tox/py39/bin/coverage run --debug=sys numbers.py
coverage_paths: /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/tests
/coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage
stdlib_paths: /usr/lib64/python3.9
third_party_paths: /coveragepy/.tox/py39/bin
/coveragepy/.tox/py39/lib64/python3.9/site-packages
/root/.local/bin
/coveragepy/.tox/py39/lib/python3.9/site-packages
/root/.local/lib64/python3.9/site-packages
/root/.local/lib/python3.9/site-packages
/coveragepy/.tox/py39/lib/python
source_match: -none-
source_pkgs_match: -none-
include_match: -none-
omit_match: -none-
cover_match: /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage
/coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/tests
pylib_match: /usr/lib64/python3.9
third_match: /coveragepy/.tox/py39/bin
/coveragepy/.tox/py39/lib64/python3.9/site-packages
/coveragepy/.tox/py39/lib/python
/coveragepy/.tox/py39/lib/python3.9/site-packages
/root/.local/bin
/root/.local/lib64/python3.9/site-packages
/root/.local/lib/python3.9/site-packages
source_in_third_match: -none-
sqlite3_sqlite_version: 3.50.2
sqlite3_temp_store: 0
sqlite3_compile_options: ATOMIC_INTRINSICS=1, COMPILER=gcc-15.1.1 20250521 (Red Hat 15.1.1-2),
DEFAULT_AUTOVACUUM, DEFAULT_CACHE_SIZE=-2000, DEFAULT_FILE_FORMAT=4,
DEFAULT_JOURNAL_SIZE_LIMIT=-1, DEFAULT_MMAP_SIZE=0, DEFAULT_PAGE_SIZE=4096,
DEFAULT_PCACHE_INITSZ=20, DEFAULT_RECURSIVE_TRIGGERS,
DEFAULT_SECTOR_SIZE=4096, DEFAULT_SYNCHRONOUS=2,
DEFAULT_WAL_AUTOCHECKPOINT=1000, DEFAULT_WAL_SYNCHRONOUS=2,
DEFAULT_WORKER_THREADS=0, DIRECT_OVERFLOW_READ, DISABLE_DIRSYNC,
ENABLE_COLUMN_METADATA, ENABLE_DBPAGE_VTAB, ENABLE_DBSTAT_VTAB,
ENABLE_FTS3, ENABLE_FTS3_PARENTHESIS, ENABLE_FTS4, ENABLE_FTS5,
ENABLE_MATH_FUNCTIONS, ENABLE_PREUPDATE_HOOK, ENABLE_RTREE, ENABLE_SESSION,
ENABLE_UNLOCK_NOTIFY, HAVE_ISNAN, MALLOC_SOFT_LIMIT=1024, MAX_ATTACHED=10,
MAX_COLUMN=2000, MAX_COMPOUND_SELECT=500, MAX_DEFAULT_PAGE_SIZE=8192,
MAX_EXPR_DEPTH=1000, MAX_FUNCTION_ARG=1000, MAX_LENGTH=1000000000,
MAX_LIKE_PATTERN_LENGTH=50000, MAX_MMAP_SIZE=0x7fff0000,
MAX_PAGE_COUNT=0xfffffffe, MAX_PAGE_SIZE=65536, MAX_SQL_LENGTH=1000000000,
MAX_TRIGGER_DEPTH=1000, MAX_VARIABLE_NUMBER=32766, MAX_VDBE_OP=250000000,
MAX_WORKER_THREADS=8, MUTEX_PTHREADS, SECURE_DELETE, SYSTEM_MALLOC,
TEMP_STORE=1, THREADSAFE=1
-- end -------------------------------------------------------
123 456
__________________________________________________ CoverageCoreTest.test_core_request_ctrace_but_missing ___________________________________________________
[gw8] linux -- Python 3.9.23 /coveragepy/.tox/py39/bin/python
self = <tests.test_process.CoverageCoreTest object at 0x7fce58d28070>
@pytest.mark.skipif(has_ctracer, reason="CTracer needs to be missing")
def test_core_request_ctrace_but_missing(self) -> None:
self.del_environ("COVERAGE_CORE")
self.make_file(".coveragerc", "[run]\ncore = ctrace\n")
self.make_file("numbers.py", "print(123, 456)")
out = self.run_command("coverage run --debug=sys,pybehave numbers.py")
assert out.endswith("123 456\n")
core = re_line(r" core:", out).strip()
> assert core == "core: PyTracer"
E AssertionError: assert 'core: CTracer' == 'core: PyTracer'
E
E - core: PyTracer
E ? ^^
E + core: CTracer
E ? ^
/coveragepy/tests/test_process.py:1363: AssertionError
------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------
-- sys -------------------------------------------------------
coverage_version: 7.10.7a0.dev1
coverage_module: /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/__init__.py
core: CTracer
CTracer: available from /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/tracer.cpython-39-x86_64-linux-gnu.so
plugins.file_tracers: -none-
plugins.configurers: -none-
plugins.context_switchers: -none-
configs_attempted: /tmp/pytest-of-root/pytest-0/popen-gw8/t29/.coveragerc
configs_read: /tmp/pytest-of-root/pytest-0/popen-gw8/t29/.coveragerc
config_file: /tmp/pytest-of-root/pytest-0/popen-gw8/t29/.coveragerc
config_contents: b'[run]\ncore = ctrace\n'
data_file: /tmp/pytest-of-root/pytest-0/popen-gw8/t29/.coverage
python: 3.9.23 (main, Jul 25 2025, 00:00:00) [GCC 15.1.1 20250521 (Red Hat 15.1.1-2)]
platform: Linux-6.12.41-gentoo-dist-x86_64-with-glibc2.42
implementation: CPython
build: main
Jul 25 2025 00:00:00
gil_enabled: True
executable: /coveragepy/.tox/py39/bin/python
def_encoding: utf-8
fs_encoding: utf-8
pid: 1668
cwd: /tmp/pytest-of-root/pytest-0/popen-gw8/t29
path: /tmp/pytest-of-root/pytest-0/popen-gw8/t29
/usr/lib64/python39.zip
/usr/lib64/python3.9
/usr/lib64/python3.9/lib-dynload
/coveragepy/.tox/py39/lib64/python3.9/site-packages
/coveragepy/.tox/py39/lib/python3.9/site-packages
environment: COVERAGE_RUN = true
COVERAGE_TESTING = True
HOME = /root
PYTEST_CURRENT_TEST = tests/test_process.py::CoverageCoreTest::test_core_request_ctrace_but_missing (call)
PYTEST_VERSION = 8.4.2
PYTEST_XDIST_TESTRUNUID = 096ea5d3b85e456996338b8b35ef51d4
PYTEST_XDIST_WORKER = gw8
PYTEST_XDIST_WORKER_COUNT = 16
PYTHONHASHSEED = 856143455
PYTHONIOENCODING = UTF-8
PYTHONWARNDEFAULTENCODING =
PYTHON_COLORS = 0
command_line: /coveragepy/.tox/py39/bin/coverage run --debug=sys,pybehave numbers.py
coverage_paths: /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/tests
/coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage
stdlib_paths: /usr/lib64/python3.9
third_party_paths: /coveragepy/.tox/py39/bin
/coveragepy/.tox/py39/lib64/python3.9/site-packages
/root/.local/bin
/coveragepy/.tox/py39/lib/python3.9/site-packages
/root/.local/lib64/python3.9/site-packages
/root/.local/lib/python3.9/site-packages
/coveragepy/.tox/py39/lib/python
source_match: -none-
source_pkgs_match: -none-
include_match: -none-
omit_match: -none-
cover_match: /coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage
/coveragepy/.tox/py39/lib64/python3.9/site-packages/coverage/tests
pylib_match: /usr/lib64/python3.9
third_match: /coveragepy/.tox/py39/bin
/coveragepy/.tox/py39/lib64/python3.9/site-packages
/coveragepy/.tox/py39/lib/python
/coveragepy/.tox/py39/lib/python3.9/site-packages
/root/.local/bin
/root/.local/lib64/python3.9/site-packages
/root/.local/lib/python3.9/site-packages
source_in_third_match: -none-
sqlite3_sqlite_version: 3.50.2
sqlite3_temp_store: 0
sqlite3_compile_options: ATOMIC_INTRINSICS=1, COMPILER=gcc-15.1.1 20250521 (Red Hat 15.1.1-2),
DEFAULT_AUTOVACUUM, DEFAULT_CACHE_SIZE=-2000, DEFAULT_FILE_FORMAT=4,
DEFAULT_JOURNAL_SIZE_LIMIT=-1, DEFAULT_MMAP_SIZE=0, DEFAULT_PAGE_SIZE=4096,
DEFAULT_PCACHE_INITSZ=20, DEFAULT_RECURSIVE_TRIGGERS,
DEFAULT_SECTOR_SIZE=4096, DEFAULT_SYNCHRONOUS=2,
DEFAULT_WAL_AUTOCHECKPOINT=1000, DEFAULT_WAL_SYNCHRONOUS=2,
DEFAULT_WORKER_THREADS=0, DIRECT_OVERFLOW_READ, DISABLE_DIRSYNC,
ENABLE_COLUMN_METADATA, ENABLE_DBPAGE_VTAB, ENABLE_DBSTAT_VTAB,
ENABLE_FTS3, ENABLE_FTS3_PARENTHESIS, ENABLE_FTS4, ENABLE_FTS5,
ENABLE_MATH_FUNCTIONS, ENABLE_PREUPDATE_HOOK, ENABLE_RTREE, ENABLE_SESSION,
ENABLE_UNLOCK_NOTIFY, HAVE_ISNAN, MALLOC_SOFT_LIMIT=1024, MAX_ATTACHED=10,
MAX_COLUMN=2000, MAX_COMPOUND_SELECT=500, MAX_DEFAULT_PAGE_SIZE=8192,
MAX_EXPR_DEPTH=1000, MAX_FUNCTION_ARG=1000, MAX_LENGTH=1000000000,
MAX_LIKE_PATTERN_LENGTH=50000, MAX_MMAP_SIZE=0x7fff0000,
MAX_PAGE_COUNT=0xfffffffe, MAX_PAGE_SIZE=65536, MAX_SQL_LENGTH=1000000000,
MAX_TRIGGER_DEPTH=1000, MAX_VARIABLE_NUMBER=32766, MAX_VDBE_OP=250000000,
MAX_WORKER_THREADS=8, MUTEX_PTHREADS, SECURE_DELETE, SYSTEM_MALLOC,
TEMP_STORE=1, THREADSAFE=1
-- pybehave --------------------------------------------------
CPYTHON: True
GIL: True
LINUX: True
MACOS: False
METACOV: False
PYPY: False
PYPYVERSION: (0,)
PYVERSION: (3, 9, 23, 'final', 0, 0)
SHIPPING_WHEELS: True
SYSMON_DEFAULT: False
TESTING: True
WINDOWS: False
branch_right_left: False
deferred_annotations: False
docstring_only_function: True
exit_through_with: False
exit_with_through_ctxmgr: False
fstring_syntax: False
keep_constant_test: False
lasti_is_yield: True
match_case: False
module_firstline_1: False
omit_after_jump: False
omit_after_return: False
optimize_if_debug: True
optimize_if_not_debug: 2
optimize_unreachable_try_else: False
pep626: False
pep669: False
soft_keywords: False
-- end -------------------------------------------------------
123 456
__________________________________________________________ VirtualenvTest.test_bug_888[coverage] ___________________________________________________________
[gw1] linux -- Python 3.9.23 /coveragepy/.tox/py39/bin/python
self = <tests.test_venv.VirtualenvTest object at 0x7f6d6d497640>, coverage_command = 'coverage'
def test_bug_888(self, coverage_command: str) -> None:
out = run_in_venv(
coverage_command + " run --source=bug888/app,bug888/plugin bug888/app/testcov/main.py",
)
# When the test fails, the output includes "Already imported a file that will be measured"
> assert out == "Plugin here\n"
E AssertionError: assert 'Plugin here\nPlugin here\n' == 'Plugin here\n'
E
E Plugin here
E + Plugin here
/coveragepy/tests/test_venv.py:405: AssertionError
------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------
Plugin here
Plugin here
_____________________________________________________ VirtualenvTest.test_bug_888[python -m coverage] ______________________________________________________
[gw1] linux -- Python 3.9.23 /coveragepy/.tox/py39/bin/python
self = <tests.test_venv.VirtualenvTest object at 0x7f6d6d497700>, coverage_command = 'python -m coverage'
def test_bug_888(self, coverage_command: str) -> None:
out = run_in_venv(
coverage_command + " run --source=bug888/app,bug888/plugin bug888/app/testcov/main.py",
)
# When the test fails, the output includes "Already imported a file that will be measured"
> assert out == "Plugin here\n"
E AssertionError: assert 'Plugin here\nPlugin here\n' == 'Plugin here\n'
E
E Plugin here
E + Plugin here
/coveragepy/tests/test_venv.py:405: AssertionError
------------------------------------------------------------------- Captured stdout call -------------------------------------------------------------------
Plugin here
Plugin here
================================================================= short test summary info ==================================================================
FAILED tests/test_process.py::CoverageCoreTest::test_core_default - AssertionError: assert 'core: CTracer' == 'core: PyTracer'
FAILED tests/test_process.py::CoverageCoreTest::test_core_request_ctrace_but_missing - AssertionError: assert 'core: CTracer' == 'core: PyTracer'
FAILED tests/test_venv.py::VirtualenvTest::test_bug_888[coverage]@virtualenv_test - AssertionError: assert 'Plugin here\nPlugin here\n' == 'Plugin here\n'
FAILED tests/test_venv.py::VirtualenvTest::test_bug_888[python -m coverage]@virtualenv_test - AssertionError: assert 'Plugin here\nPlugin here\n' == 'Plugin here\n'
4 failed, 1442 passed, 62 skipped, 1 xfailed in 16.49s
py39: exit 1 (16.88 seconds) /coveragepy> python igor.py test_with_core pytrace pid=155
py39: FAIL ✖ in 29.29 seconds