Coverage data file under pytest cache

Coverage Data File Under .pytest_cache

When to use

You run tests with pytest -n auto --cov and end up with dozens of .coverage.<hostname>.<pid>.<random> files at the repo root. They look like garbage, accidentally get committed, and clutter git status. There's a one-line fix.

How it works

Set tool.coverage.run.data_file to a path inside .pytest_cache/. pytest-xdist appends host/pid/random suffixes to whatever you set, so all the fragments land inside the already-gitignored cache directory.

Example

[tool.coverage.run]
# With pytest-xdist (-n auto), each worker writes a fragment; put them under
# .pytest_cache/ (already gitignored) instead of .coverage.<hostname>.* at repo root.
data_file = ".pytest_cache/.coverage"

Combine with a Makefile clean target that explicitly nukes leftovers from older runs:

clean:
    find . -maxdepth 1 \( -name '.coverage' -o -name '.coverage.*' \) -delete 2>/dev/null || true

Gotchas

• .pytest_cache/ is gitignored by default in most Python templates; verify yours has it.
• If you use coverage combine separately (e.g. in CI to merge fragments from parallel jobs), point its input/output paths at the same .pytest_cache/.coverage location.
• Doesn't change behaviour for single-worker pytest --cov — it just keeps the folder tidy.