pytest-xdist-installed-but-not-used

Detects CI pytest commands that run without parallel workers despite pytest-xdist being installed.

Why it matters

pytest-xdist can significantly reduce wall-clock time for large test suites by distributing tests across CPU cores. Since the project already includes pytest-xdist as a dependency, parallel execution was likely intended but not enabled in CI.

Detection

Reports when all of the following are true:

• CI command runs pytest directly (not via tox/nox/make)
• pytest-xdist is installed in project dependencies
• pytest command does not use -n or --numprocesses
• pytest config does not enable xdist via addopts
• Test suite appears non-trivial (30+ test files in a test directory)

Commands are evaluated separately, including python -m pytest and uv/Poetry/PDM run wrappers. Static workflow/job/step env values are merged with step precedence before checking flags; unknown expansion prevents a claim that parallel workers are absent. Locations identify the actual run command, rather than the workflow’s first line.

Exclusions

Does not report when:

• -n / --numprocesses is present in the command
• pytest config already sets addopts = -n auto
• Command targets a single test file or test node, including example _tests.py files
• Command uses serial-only flags (--pdb, --trace, --forked, -s, --capture=no)
• Command targets integration/e2e/smoke markers (-m integration, etc.)
• Command runs via a wrapper (tox, nox, make test, npm test, just test)

Severity

warning — the project already opted into pytest-xdist but is not using it in CI.