Fix test isolation and coverage for PyPy and macOS

Author: Евгений Блинов

.github/workflows/tests_and_coverage.yml

@@ -60,7 +60,20 @@ jobs:
       shell: bash
       run: pip list
 
-    - name: Run tests and show the branch coverage on the command line
+    - name: Run tests and show the branch coverage on the command line (CPython)
+      if: "!startsWith(matrix.python-version, 'pypy')"
+      shell: bash
+      run: |
+        pth_file="$(python -c 'import sysconfig; print(sysconfig.get_path("purelib"))')/suby_coverage_process_startup.pth"
+        printf "import os; os.getenv('COVERAGE_PROCESS_START') and __import__('coverage').process_startup()\n" > "$pth_file"
+        coverage erase
+        COVERAGE_PROCESS_START="$PWD/pyproject.toml" coverage run -m pytest -p no:cov -n auto --cache-clear --assert=plain
+        coverage combine
+        coverage report -m --fail-under=100 --omit='*tests*'
+        coverage xml --omit='*tests*'
+
+    - name: Run tests and show the branch coverage on the command line (PyPy)
+      if: startsWith(matrix.python-version, 'pypy')
       shell: bash
       run: pytest --cov=suby --cov-branch --cov-report=term-missing --cov-report=xml:coverage.xml --cov-fail-under=100 -n auto --cache-clear --assert=plain
 

tests/conftest.py

@@ -10,12 +10,14 @@
 
 
 def pytest_configure(config):
-    """Prevent child processes spawned by run() from inheriting pytest-cov's subprocess coverage.
+    """Prevent child processes spawned by run() from inheriting subprocess coverage hooks.
 
-    Without this, every short-lived Python subprocess spawned by the test suite inherits COV_CORE_*
-    environment variables, causing pytest-cov's .pth hook to activate coverage in each child process.
+    Without this, every short-lived Python subprocess spawned by the test suite inherits coverage
+    environment variables (COVERAGE_PROCESS_START for coverage run, COV_CORE_* for pytest-cov),
+    causing coverage to activate in each child process and slowing the suite significantly.
     """
     if hasattr(config, 'workerinput'):
+        os.environ.pop('COVERAGE_PROCESS_START', None)
         for key in list(os.environ):
             if key.startswith('COV_CORE_'):
                 os.environ.pop(key)

tests/units/test_process_waiting.py

@@ -27,6 +27,7 @@
 _is_event_driven_platform = has_event_driven_wait()
 _is_macos = sys.platform == 'darwin'
 _is_linux = sys.platform == 'linux'
+_is_pypy = sys.implementation.name == 'pypy'
 _has_pidfd = hasattr(os, 'pidfd_open')
 _COORDINATION_TIMEOUT_SECONDS = 5.0
 
@@ -207,7 +208,7 @@ def test_oserror_fallback_with_reaped_pid():
 @pytest.mark.parametrize(
     'expected',
     [
-        pytest.param(True, marks=pytest.mark.skipif(not _is_macos, reason='macOS only')),
+        pytest.param(True, marks=pytest.mark.skipif(not _is_macos or _is_pypy, reason='macOS CPython only')),
         pytest.param(True, marks=pytest.mark.skipif(not (_is_linux and _has_pidfd), reason='Linux 3.9+ only')),
         pytest.param(False, marks=pytest.mark.skipif(_is_event_driven_platform, reason='Only for fallback platforms')),
     ],
@@ -315,7 +316,7 @@ def worker():
 @pytest.mark.parametrize(
     'waiter_name',
     [
-        pytest.param('_wait_kqueue', marks=pytest.mark.skipif(not _is_macos, reason='macOS only')),
+        pytest.param('_wait_kqueue', marks=pytest.mark.skipif(not _is_macos or _is_pypy, reason='macOS CPython only')),
         pytest.param('_wait_pidfd', marks=pytest.mark.skipif(not (_is_linux and _has_pidfd), reason='Linux 3.9+ only')),
     ],
 )
@@ -337,7 +338,7 @@ def test_platform_waiter_directly_returns_without_killing_running_process(waiter
         process.wait()
 
 
-@pytest.mark.skipif(not _is_macos, reason='macOS only')
+@pytest.mark.skipif(not _is_macos or _is_pypy, reason='macOS CPython only')
 def test_macos_wait_for_process_exit_passes_none_to_event_driven_waiter():
     """On macOS, None timeout is forwarded to the event-driven waiter unchanged."""
     process = subprocess.Popen(
@@ -353,7 +354,7 @@ def test_macos_wait_for_process_exit_passes_none_to_event_driven_waiter():
         process.wait()
 
 
-@pytest.mark.skipif(not _is_macos, reason='macOS only')
+@pytest.mark.skipif(not _is_macos or _is_pypy, reason='macOS CPython only')
 def test_macos_wait_kqueue_builds_subscription_and_closes_queue():
     """The macOS kqueue waiter subscribes to the child-process exit event and closes the kqueue handle afterwards."""
     mock_kqueue = MagicMock()
@@ -375,7 +376,7 @@ def test_macos_wait_kqueue_builds_subscription_and_closes_queue():
     mock_kqueue.close.assert_called_once()
 
 
-@pytest.mark.skipif(not _is_macos, reason='macOS only')
+@pytest.mark.skipif(not _is_macos or _is_pypy, reason='macOS CPython only')
 def test_macos_wait_for_process_exit_falls_back_after_kqueue_oserror():
     """If the macOS waiter raises OSError, wait_for_process_exit falls back to process.wait()."""
     process = subprocess.Popen(