pytest-forked was removed from requirements-testing.txt, and tox.jinja only re-adds it for the common and gevent test environments (common: pytest-forked). The opentelemetry, otlp, and potel envs (defined at tox.jinja lines 124-131) only declare opentelemetry-distro and do not include pytest-forked. Those envs run tests/integrations/opentelemetry/ (via _TESTPATH), where tests such as test_propagator.py and test_experimental.py use @pytest.mark.forked to isolate global-state mutation. Since there is no --strict-markers config (pyproject.toml markers only lists tests_internal_exceptions), the unknown forked marker is silently ignored and those tests run in-process, defeating the intended isolation and risking cross-test pollution/flakiness.

Also found at:

• scripts/populate_tox/config.py:186

After removing pytest-forked from requirements-testing.txt, the gevent and opentelemetry tox environments have no path to install it, yet both contain tests decorated with @pytest.mark.forked that require process isolation.

Also found at:

• scripts/populate_tox/config.py:378