prevent capteesys from duplicating output when -s disables global capture #13796
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bluetech
reviewed
Oct 7, 2025
| from _pytest.fixtures import SubRequest | ||
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| def test_dummy_test_with_traceback( |
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This test doesn't seem to do anything. I suggest looking at other tests in testing/test_capture.py and adding a test there.
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Summary
Using the
capteesysfixture with-s(--capture=no) printed output twice, even if the fixture wasn’t used in the test body. This issue is tracked in [pytest-dev/pytest#13784](#13784) and is fixed by this PR.Fixes: #13784
Root Cause
capteesysalways instantiated a tee-ingSysCapture, so when global capture was disabled (-s), output went directly to the terminal and was also duplicated through the tee path.Fix
Enable tee only when global capture is active. When global capture is disabled,
capteesysyields a non-teeing fixture to avoid duplication.Changes localized to:
src/_pytest/capture.py(capteesysfixture)Tests
Added regression test:
test_capteesys_issue.py-sand validates the fix.Behavior Comparison
Before:
Running
pytest -swithcapteesysin the test signature duplicatedstdout/stderr.After:
pytest -sprints each line exactly once (no duplication).With capture enabled,
capteesyscontinues to tee and capture as expected.Backwards Compatibility
--capturemode.Affected Files
src/_pytest/capture.pytest_capteesys_issue.py