Update.

Author: tsalo

test/conftest.py

@@ -0,0 +1,13 @@
+"""Pytest hooks shared by this package's tests."""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+# CLI tests run subprocesses with cwd under tmp_path (outside the repo). Coverage
+# discovers [tool.coverage] from the process cwd, so those children would default to
+# line-only / non-parallel data and pytest-cov then fails on combine with arc data from
+# the parent. Point subprocess coverage at the project config explicitly.
+_ROOT = Path(__file__).resolve().parents[1]
+os.environ.setdefault('COVERAGE_RCFILE', str(_ROOT / 'pyproject.toml'))

tox.ini

@@ -45,7 +45,7 @@ uv_resolution =
   min: lowest-direct
 
 commands =
-  pytest -m "not s3" --cov=modelarrayio --cov-report=term-missing --cov-report=xml {posargs:test}
+  pytest -m "not s3" --cov=modelarrayio --cov-config={toxinidir}/pyproject.toml --cov-report=term-missing --cov-report=xml {posargs:test}
 
 [testenv:lint]
 runner = uv-venv-lock-runner