Fix silently-passing subprocess tests and process resource leak (#112)

* Fix PicklingError in subprocess spawn by moving fixtures to conftest.py

Co-authored-by: lostmsu <239520+lostmsu@users.noreply.github.com>

* Fix silent subprocess failures: assert exitcode and fix test_coreclr_properties kwargs

The real reason CI doesn't fail despite Python 3.13 being tested:
run_in_subprocess never checked p.exitcode, so any subprocess crash was
silently ignored by the parent test.

Adding the assert immediately exposes a pre-existing bug:
test_coreclr_properties passed properties=dict(...) as a single kwarg,
but _do_test_coreclr_autogenerated_runtimeconfig uses **properties to
collect individual kwargs. This double-wrapped the dict, causing
AttributeError: 'dict' object has no attribute 'encode' in the subprocess
— silently swallowed until now.

Co-authored-by: lostmsu <239520+lostmsu@users.noreply.github.com>

* Fix resource leak: wrap p.exitcode assert in try/finally so p.close() always runs

Without try/finally, if `assert p.exitcode == 0` raises AssertionError,
`p.close()` is never called. This leaves the Process object unclosed
and causes `ResourceWarning: process ... not closed` on Python 3.12+.

Co-authored-by: lostmsu <239520+lostmsu@users.noreply.github.com>

* Fix format

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: lostmsu <239520+lostmsu@users.noreply.github.com>
Co-authored-by: Benedikt Reinartz <filmor@gmail.com>

Author: 3 people

tests/conftest.py

@@ -0,0 +1,25 @@
+from pathlib import Path
+from subprocess import check_call
+
+import pytest
+
+NETCORE_VERSION = "net10.0"
+
+
+@pytest.fixture(scope="session")
+def example_netstandard(tmp_path_factory: pytest.TempPathFactory) -> Path:
+    return build_example(tmp_path_factory, "netstandard2.0")
+
+
+@pytest.fixture(scope="session")
+def example_netcore(tmp_path_factory: pytest.TempPathFactory) -> Path:
+    return build_example(tmp_path_factory, NETCORE_VERSION)
+
+
+def build_example(tmp_path_factory: pytest.TempPathFactory, framework: str) -> Path:
+    out = tmp_path_factory.mktemp(f"example-{framework}")
+    proj_path = Path(__file__).parent.parent / "example" / "example.csproj"
+
+    _ = check_call(["dotnet", "build", str(proj_path), "-o", str(out), "-f", framework])
+
+    return out

tests/test_common.py

@@ -1,31 +1,9 @@
 import shutil
 import sys
 from pathlib import Path
-from subprocess import check_call
 
 import pytest
 
-NETCORE_VERSION = "net10.0"
-
-
-@pytest.fixture(scope="session")
-def example_netstandard(tmp_path_factory: pytest.TempPathFactory) -> Path:
-    return build_example(tmp_path_factory, "netstandard2.0")
-
-
-@pytest.fixture(scope="session")
-def example_netcore(tmp_path_factory: pytest.TempPathFactory) -> Path:
-    return build_example(tmp_path_factory, NETCORE_VERSION)
-
-
-def build_example(tmp_path_factory: pytest.TempPathFactory, framework: str) -> Path:
-    out = tmp_path_factory.mktemp(f"example-{framework}")
-    proj_path = Path(__file__).parent.parent / "example" / "example.csproj"
-
-    _ = check_call(["dotnet", "build", str(proj_path), "-o", str(out), "-f", framework])
-
-    return out
-
 
 def test_mono(example_netstandard: Path):
     from clr_loader import get_mono
@@ -112,7 +90,7 @@ def test_coreclr_properties(example_netcore: Path):
     run_in_subprocess(
         _do_test_coreclr_autogenerated_runtimeconfig,
         example_netcore,
-        properties=dict(APP_CONTEXT_BASE_DIRECTORY=str(example_netcore)),
+        APP_CONTEXT_BASE_DIRECTORY=str(example_netcore),
     )
 
 
@@ -177,4 +155,9 @@ def run_in_subprocess(func, *args, **kwargs):
     p = get_context("spawn").Process(target=func, args=args, kwargs=kwargs)
     p.start()
     p.join()
-    p.close()
+    try:
+        assert p.exitcode == 0, (
+            f"Subprocess {func.__name__!r} failed with exit code {p.exitcode}"
+        )
+    finally:
+        p.close()