tests: better support for parallel testing

tests/conftest.py

@@ -12,11 +12,17 @@
 import tempfile
 
 from functools import partial, update_wrapper
+from pathlib import Path
 
 import pytest
 
 import build.env
 
+if sys.version_info < (3, 11):
+    import tomli as tomllib
+else:
+    import tomllib
+
 
 def pytest_addoption(parser):
     os.environ['PYTHONWARNINGS'] = 'ignore:DEPRECATION::pip._internal.cli.base_command'  # for when not run within tox
@@ -101,10 +107,29 @@ def packages_path():
     return os.path.realpath(os.path.join(__file__, '..', 'packages'))
 
 
+def is_setuptools(package_path):
+    if package_path.joinpath("setup.py").is_file():
+        return True
+    pyproject = package_path / "pyproject.toml"
+    try:
+        with pyproject.open("rb") as f:
+            pp = tomllib.load(f)
+    except (FileNotFoundError, ValueError):
+        return True
+    return "setuptools" in pp.get("build-system", {}).get("build-backend", "setuptools")
+
+
+
 def generate_package_path_fixture(package_name):
     @pytest.fixture
-    def fixture(packages_path):
-        return os.path.join(packages_path, package_name)
+    def fixture(packages_path, tmp_path):
+        package_path = Path(packages_path) / package_name
+        if not is_setuptools(package_path):
+            return str(package_path)
+
+        new_path = tmp_path / package_name
+        shutil.copytree(package_path, new_path)
+        return str(new_path)
 
     return fixture