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test: ignore Python 3.15 fork-with-threads DeprecationWarning in test_multiprocessing #4143

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Merged
d-v-b merged 2 commits into from
Jul 13, 2026
Merged

test: ignore Python 3.15 fork-with-threads DeprecationWarning in test_multiprocessing #4143

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test: ignore Python 3.15 fork-with-threads DeprecationWarning in test…
d-v-b Jul 13, 2026
6673752
Merge branch 'main' into claude/zarr-python-4086-8cc808
d-v-b Jul 13, 2026
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1 change: 1 addition & 0 deletions changes/4086.misc.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix `test_multiprocessing[fork]` failing on Python 3.15, where `os.fork()` in a multi-threaded process emits a `DeprecationWarning` that the test suite promotes to an error.
15 changes: 12 additions & 3 deletions tests/test_array.py
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Expand Up @@ -1903,9 +1903,18 @@ def _index_array(arr: AnyArray, index: Any) -> Any:
[
pytest.param(
"fork",
marks=pytest.mark.skipif(
sys.platform in ("win32", "darwin"), reason="fork not supported on Windows or OSX"
),
marks=[
pytest.mark.skipif(
sys.platform in ("win32", "darwin"),
reason="fork not supported on Windows or OSX",
),
# Python 3.15 deprecates fork() in multi-threaded processes, and zarr's
# sync event-loop thread is always running here. Fork-safety despite
# those threads is exactly what this test pins down, so keep running it.
pytest.mark.filterwarnings(
r"ignore:This process \(pid=\d+\) is multi-threaded, use of fork\(\):DeprecationWarning"
),
],
),
"spawn",
pytest.param(
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