ci(test): enable pytest-xdist for cuopt Python tests

[ramakrishnap-nv]

Summary

• Add pytest-xdist to test_python_common dependencies (propagated to conda envs and pyproject.toml files via dependency file generator)
• Pass -n auto to the non-nightly cuopt pytest invocation in ci/run_cuopt_pytests.sh
• Server tests (run_cuopt_server_pytests.sh) are unchanged — they bind a fixed port (localhost:18900) that would conflict across parallel workers

The script already cds into python/cuopt/cuopt where xdist + coverage is known to work (noted in the existing comment on line 7).

Test plan

• CI conda-python-tests job shows parallel test workers in the log
• Test results and coverage report are complete (no missing tests)
• conda-python-tests wall time is reduced compared to baseline
• Server tests are unaffected

🤖 Generated with Claude Code

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[ramakrishnap-nv]

/ok to test eb9a30f

[github-actions]

CI Test Summary

✅ All 31 test job(s) passed.

[ramakrishnap-nv]

/ok to test 10d42be

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds pytest-xdist to conda and pyproject test dependencies, runs non-nightly CI pytest jobs with -n 2, and updates cuOpt test server port selection to derive worker-specific ports from PYTEST_XDIST_WORKER.

Changes

pytest-xdist Parallel Test Execution

Layer / File(s)	Summary
Add pytest-xdist dependency declarations conda/environments/all_cuda-129_arch-aarch64.yaml, conda/environments/all_cuda-129_arch-x86_64.yaml, conda/environments/all_cuda-133_arch-aarch64.yaml, conda/environments/all_cuda-133_arch-x86_64.yaml, dependencies.yaml, python/cuopt/pyproject.toml, python/cuopt_self_hosted/pyproject.toml, python/cuopt_server/pyproject.toml	Adds pytest-xdist to conda environment dependency lists, the shared test_python_common package group, and test optional-dependencies in the cuopt, cuopt_self_hosted, and cuopt_server pyproject.toml files.
Enable parallel test execution and worker-aware ports ci/run_cuopt_pytests.sh, ci/run_cuopt_server_pytests.sh, python/cuopt/cuopt/tests/linear_programming/test_cpu_only_execution.py, python/cuopt_server/cuopt_server/tests/utils/utils.py	Changes the non-nightly pytest commands in both CI scripts to use -n 2, adds worker-aware port calculation from PYTEST_XDIST_WORKER, and uses that port for the cuOpt server subprocess and default client port in tests.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• NVIDIA/cuopt#722: Both PRs modify the cuopt test-run CI scripts and change how pytest is invoked in CI, including pytest-xdist usage.

Suggested reviewers

• jameslamb

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: enabling pytest-xdist for cuopt Python tests.
Description check	✅ Passed	The description is on-topic and describes the xdist dependency and pytest parallelization changes.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/pytest-xdist-python-tests

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[coderabbitai]

🧹 Nitpick comments (2)

python/cuopt_server/cuopt_server/tests/utils/utils.py (2)

20-23: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Duplicate worker-id parsing logic across test files.

The PYTEST_XDIST_WORKER → worker-id parsing here is essentially duplicated from python/cuopt/cuopt/tests/linear_programming/test_cpu_only_execution.py (_start_grpc_server_fixture). Consider extracting a shared helper (e.g., in a common test-utils module or xdist's own worker_id fixture/get_xdist_worker_id()) instead of reimplementing the gwN parsing in two places.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@python/cuopt_server/cuopt_server/tests/utils/utils.py` around lines 20 - 23,
The worker-id parsing logic in _worker_port duplicates the same
PYTEST_XDIST_WORKER handling already present in _start_grpc_server_fixture, so
refactor both call sites to use a shared helper instead of re-parsing gwN in
multiple tests. Move the worker id extraction into a common test utility module
or switch both places to xdist’s built-in worker-id support (for example a
helper like get_xdist_worker_id() or the worker_id fixture), and update
_worker_port to consume that shared helper.

---

368-368: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Default port computed at import time, not call time.

port=_worker_port() is evaluated once when the class is defined (module import), unlike cuoptproc's use of _worker_port() at fixture-execution time. This happens to work today because PYTEST_XDIST_WORKER is set before worker-side test collection, but it's a fragile pattern relative to the runtime evaluation used elsewhere in this same file.

♻️ Suggested fix for lazy evaluation

-    def __init__(self, port=_worker_port()):
+    def __init__(self, port=None):
+        if port is None:
+            port = _worker_port()

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@python/cuopt_server/cuopt_server/tests/utils/utils.py` at line 368, The
default port for the class initializer is being computed too early because
__init__ uses port=_worker_port() at definition/import time instead of when an
instance is created. Update the initializer so _worker_port() is called lazily
inside the constructor path, matching the runtime evaluation pattern used by
cuoptproc in this file, and keep the default behavior unchanged for callers that
do not pass an explicit port.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@python/cuopt_server/cuopt_server/tests/utils/utils.py`:
- Around line 20-23: The worker-id parsing logic in _worker_port duplicates the
same PYTEST_XDIST_WORKER handling already present in _start_grpc_server_fixture,
so refactor both call sites to use a shared helper instead of re-parsing gwN in
multiple tests. Move the worker id extraction into a common test utility module
or switch both places to xdist’s built-in worker-id support (for example a
helper like get_xdist_worker_id() or the worker_id fixture), and update
_worker_port to consume that shared helper.
- Line 368: The default port for the class initializer is being computed too
early because __init__ uses port=_worker_port() at definition/import time
instead of when an instance is created. Update the initializer so _worker_port()
is called lazily inside the constructor path, matching the runtime evaluation
pattern used by cuoptproc in this file, and keep the default behavior unchanged
for callers that do not pass an explicit port.

---

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📥 Commits

Reviewing files that changed from the base of the PR and between 792b2f4 and ade01f2.

📒 Files selected for processing (2)

• ci/run_cuopt_server_pytests.sh
• python/cuopt_server/cuopt_server/tests/utils/utils.py