perf(test): use Python’s system monitoring facilities to improve performance of test runs (#933)

Author: jenstroeger

.pre-commit-config.yaml

@@ -160,12 +160,14 @@ repos:
   hooks:
   - id: actionlint
 
-# On push to the remote, run the unit tests.
+# On push to the remote, run the unit tests. Note that the `COVERAGE_CORE` variable is
+# required for Python 3.12+ to make sure Coverage uses the new Python monitoring module.
+# See also: https://blog.trailofbits.com/2025/05/01/making-pypis-test-suite-81-faster/#optimizing-coverage-with-python-312s-sysmonitoring
 - repo: local
   hooks:
   - id: pytest
     name: Run unit tests
-    entry: pytest -c pyproject.toml --cov-config pyproject.toml src/package/ tests/ docs/
+    entry: env COVERAGE_CORE=sysmon pytest -c pyproject.toml --cov-config pyproject.toml src/package/ tests/ docs/
     language: python
     verbose: true
     always_run: true

pyproject.toml

@@ -61,12 +61,13 @@ hooks = [
 ]
 # Note that the `custom_exit_code` and `env` plugins may currently be unmaintained.
 test = [
+    "coverage ==7.6.12; python_version<'3.14'",  # https://github.com/pypi/warehouse/pull/17872#issuecomment-2845932281
     "faker ==37.6.0",
     "hypothesis >=6.21.0,<6.138.17",
     "pytest >=7.2.0,<9.0.0",
     "pytest-cases ==3.9.1",
     "pytest-custom_exit_code ==0.3.0",
-    "pytest-cov ==7.0.0",
+    "pytest-cov ==6.3.0",  # Uses: coverage[toml] >=7.5
     "pytest-doctestplus ==1.4.0",
     "pytest-env ==1.1.5",
 ]
@@ -271,6 +272,11 @@ env = [
 filterwarnings = [
     "error",
     "always::DeprecationWarning",
+    # The CoverageWarning warning is issued in two contexts:
+    # Python 3.10, 3.11: sys.monitoring isn't available in this version, using default core (no-sysmon)
+    # Python 3.12, 3.13: sys.monitoring can't measure branches in this version, using default core (no-sysmon)
+    "ignore:sys.monitoring isn't available in this version:coverage.exceptions.CoverageWarning",
+    "always::coverage.exceptions.CoverageWarning",
     # https://docs.pytest.org/en/latest/how-to/failures.html#warning-about-unraisable-exceptions-and-unhandled-thread-exceptions
     "error::pytest.PytestUnraisableExceptionWarning",
     "error::pytest.PytestUnhandledThreadExceptionWarning",