test: speed up pytest runs with xdist

.github/workflows/lint-and-test.yml

@@ -47,4 +47,4 @@ jobs:
         run: uv sync --all-extras
 
       - name: Run pytest
-        run: uv run pytest --cov=mitreattack
+        run: uv run --extra dev pytest -n 2 --cov=mitreattack

AGENTS.md

@@ -16,7 +16,9 @@
 - Before committing, run `just lint`.
 - `just lint`: run pre-commit hooks across the repo.
 - `just test`: run the pytest suite.
+- `just test-xdist`: run the pytest suite in parallel.
 - `just test-cov`: run tests with coverage for `mitreattack`.
+- `just test-cov-xdist`: run tests with coverage in parallel.
 - `just build`: build distributions with `uv build`.
 - Without `just`, run the same tools through `uv run ...`.
 
@@ -32,6 +34,10 @@
 - Framework: `pytest` (with `pytest-cov` for coverage checks).
 - Place tests under `tests/` and name files/functions `test_*.py` / `test_*`.
 - Add or update tests for behavior changes, especially around STIX parsing and changelog/diff output paths.
+- Tests that need real ATT&CK STIX data should use the shared STIX fixtures instead of downloading or
+  preparing bundles directly.
+- Parallel runs warm the shared STIX cache before workers start; update `DEFAULT_ATTACK_STIX_PREP` in
+  `tests/conftest.py` if a new xdist-backed test needs another ATT&CK release.
 - Run `just test` locally before opening a PR; use `just test-cov` for larger changes.
 
 ## Commit & Pull Request Guidelines

docs/CONTRIBUTING.md

@@ -52,10 +52,17 @@ Run `just` with no arguments to see all available commands. Here are the most co
 ```bash
 just lint          # Run pre-commit hooks (ruff format) on all files
 just test          # Run tests
+just test-xdist    # Run tests in parallel
 just test-cov      # Run tests with coverage report
+just test-cov-xdist  # Run tests with coverage in parallel
 just build         # Build the package
 ```
 
+Tests that need real ATT&CK STIX data should use the shared STIX fixtures instead of downloading or
+preparing bundles directly. Parallel test runs warm the shared STIX cache before workers start; if a
+new xdist-backed test needs an additional ATT&CK release, update the cache warmup list in
+`tests/conftest.py`.
+
 To run STIX-backed tests against specific local bundles, pass the bundle paths to pytest:
 
 ```bash

justfile

@@ -35,6 +35,14 @@ ruff-format:
 test:
     uv run pytest
 
+# Run tests in parallel
+test-xdist workers="auto":
+    uv run --extra dev pytest -n {{ workers }}
+
+# Run tests with coverage in parallel
+test-cov-xdist workers="auto":
+    uv run --extra dev pytest -n {{ workers }} --cov=mitreattack
+
 # Run tests with coverage
 test-cov:
     uv run pytest --cov=mitreattack

pyproject.toml

@@ -57,6 +57,7 @@ dev = [
     "pytest>=8.4.2",
     "pytest-cov>=7.0.0",
     "pytest-dotenv>=0.5.2",
+    "pytest-xdist>=3.8.0",
     "python-semantic-release>=10.5.0",
     "responses>=0.25.8",
     "ruff>=0.14.2",
@@ -131,3 +132,7 @@ version_files = [
     "docs/conf.py:^release = ['\"](.*)['\"]",
     "mitreattack/__init__.py:^__version__ = ['\"](.*)['\"]",
 ]
+
+[[tool.uv.index]]
+url = "https://pypi.org/simple"
+default = true

tests/changelog/conftest.py

@@ -1594,10 +1594,10 @@ def golden_161_170_changelog_dir():
 
 
 @pytest.fixture(scope="session")
-def generated_161_170_diffstix(tmp_path_factory) -> DiffStix:
+def generated_161_170_diffstix() -> DiffStix:
     """Create and cache a DiffStix instance for reuse across tests."""
     versions_param = ["16.1", "17.0"]
-    result_paths = _download_attack_stix_data(versions_param, tmp_path_factory)
+    result_paths = _download_attack_stix_data(versions_param)
     return DiffStix(
         domains=["enterprise-attack", "mobile-attack", "ics-attack"],
         old=result_paths["16.1"],