## Summary With `pytest==9.2.0` (released 2026-10-27) and `pytest-forked==1.7.5` (the latest release), every forked test fails, whether it passes, fails or is skipped: test_x.py:3: running the test EXITED with status 3 Unforked tests are unaffected. `pytest==9.1.1` with the same pytest-forked works. PyTango is affected too: `pyproject.toml` has an unpinned `pytest` and `addopts = "... --forked"`. Only one group of jobs gets pytest 9.2.0 today: the wheel test jobs (`.linux-test-wheel`, `.macos-test-wheel`), which `pip install` the `[tests]` extra from PyPI. They run on pushes to `develop` and on tags, so the next merge or release will fail. The micromamba jobs install pytest from conda-forge without a version and will break once conda-forge publishes 9.2.0 (still 9.1.1 as of 2026-10-28). The pixi jobs are safe while `pixi.lock` holds pytest 9.1.1. Windows does not use `--forked`. Downstream device servers whose tests follow the testing docs and use `@pytest.mark.forked` around `DeviceTestContext` are affected the same way. That is how we found it, in a MAX IV device server whose CI installs pytest unpinned. ## Reproduction python -m venv v && v/bin/pip install "pytest==9.2.0" "pytest-forked==1.7.5" # test_forked.py import pytest @pytest.mark.forked def test_forked_passes(): assert True v/bin/python -m pytest test_forked.py # 1 failed Python 3.14.8, Linux. ## Cause pytest 9.2 made `TestReport.nodeid` a property backed by a new `_id` attribute holding a `_pytest.nodeid.NodeId` dataclass. pytest-forked's `serialize_report()` copies `rep.__dict__` as is, so `marshal.dumps()` in the forked child raises `ValueError: unmarshallable object`. The child catches the exception and calls `os._exit(3)` without printing a traceback, so all the parent sees is "status 3". pytest's own `_report_to_json()` already converts `_id` back to a `nodeid` string; pytest-forked's copy of that code never got the change. ## Upstream status - Fix proposed in pytest-forked PR #112: https://github.com/pytest-dev/pytest-forked/pull/112 (opened 2026-10-28, not merged). - pytest-forked has merged nothing since 1.7.5 (2026-08-08), and other PRs have been open for months, so a fixed release may take a while. - Not a pytest bug: the `NodeId` change is intentional. ## Workarounds 1. Pin `pytest<9.2` in the test dependencies, until pytest-forked releases a fix. 2. Or, in `conftest.py`, patch the serializer (tested on pytest 9.1.1 and 9.2.0, with passing, failing, skipped, parametrized and class-based forked tests): import pytest_forked _serialize_report = pytest_forked.serialize_report def _serialize_report_nodeid(rep): d = _serialize_report(rep) if "_id" in d: # pytest >= 9.2 d["nodeid"] = str(d.pop("_id")) return d pytest_forked.serialize_report = _serialize_report_nodeid ## Suggestion for PyTango - Pin `pytest<9.2` in the `tests` extra in `pyproject.toml` and in the micromamba installs in `.linux-gitlab-ci.yml`, or apply the conftest patch above, until pytest-forked ships a fix. - Consider a note in `doc/how-to/testing/` next to the pytest-forked recommendation. - Related: !1070 removes `--forked` from the default test options, which would avoid this in PyTango's own suite. Its description says `--forked` "still works", which holds only below pytest 9.2.