[https://nvbugs/6337235][test] Fix MX/GMS model loader fixtures

[chienchunhung]

Description

Fix stale MX/GMS ModelLoader unit-test fixtures exposed by the expanded L0 unit-test coverage.

ModelLoader.load() now builds a SourceIdentity for GMS and MX paths. These branch-focused tests stub _load_and_validate_config() with a lightweight SimpleNamespace, so the real fingerprint builder can fail before the tests reach the GMS/MX behavior they are meant to cover. This PR stubs SourceIdentity.from_model_config() in those tests with a fixed real SourceIdentity, and makes the GMS RO backend return the same identity so the strict RO gate still executes successfully.

Reference: https://nvbugs/6337235

Test Coverage

• PYTHONPYCACHEPREFIX=/private/tmp/trtllm_pycache python3 -m py_compile tests/unittest/_torch/pyexecutor/test_model_loader_gms.py tests/unittest/_torch/pyexecutor/test_model_loader_mx.py
• git diff --check
• Commit hooks passed for the touched files. Skipped waive list check and validate-test-lists locally because they crash under this machine's Python 3.9 while parsing Python 3.10 union annotations in scripts/check_test_list.py.

Note: focused pytest was not runnable in this local environment because pytest is not installed for the system Python.

Summary by CodeRabbit

• Tests
  • Enhanced model loader test coverage to verify that the source_identity parameter is correctly passed and handled throughout the loading pipeline.

[chienchunhung]

/bot run --disable-fail-fast

[tensorrt-cicd]

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PR_Github #54892 [ run ] completed with state FAILURE. Commit: 9688833
/LLM/main/L0_MergeRequest_PR pipeline #43896 completed with status: 'FAILURE'

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[chienchunhung]

/bot run

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PR_Github #54992 [ run ] triggered by Bot. Commit: 1b115c0 Link to invocation

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PR_Github #54992 [ run ] completed with state SUCCESS. Commit: 1b115c0
/LLM/main/L0_MergeRequest_PR pipeline #43984 completed with status: 'FAILURE'

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[chienchunhung]

/bot run --disable-fail-fast

[tensorrt-cicd]

PR_Github #55009 [ run ] triggered by Bot. Commit: 1b115c0 Link to invocation

[tensorrt-cicd]

PR_Github #55009 [ run ] completed with state SUCCESS. Commit: 1b115c0
/LLM/main/L0_MergeRequest_PR pipeline #44001 completed with status: 'FAILURE'

CI Report

⚠️ Action Required:

• Please check the failed tests and fix your PR
• If you cannot view the failures, ask the CI triggerer to share details
• Once fixed, request an NVIDIA team member to trigger CI again

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[chienchunhung]

/bot reuse-pipeline

[tensorrt-cicd]

PR_Github #55063 [ reuse-pipeline ] triggered by Bot. Commit: 5ec5c41 Link to invocation

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PR_Github #55063 [ reuse-pipeline ] completed with state SUCCESS. Commit: 5ec5c41
Can't reuse PR_Github #55009 with status: FAILED

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[chienchunhung]

/bot run

[tensorrt-cicd]

PR_Github #55068 [ run ] triggered by Bot. Commit: 5ec5c41 Link to invocation

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Run ID: e0530b8f-8112-4b1b-bdd9-6d5eb46ba525

📥 Commits

Reviewing files that changed from the base of the PR and between eddaa3a and 5ec5c41.

📒 Files selected for processing (2)

• tests/unittest/_torch/pyexecutor/test_model_loader_gms.py
• tests/unittest/_torch/pyexecutor/test_model_loader_mx.py

---

📝 Walkthrough

Walkthrough

Two test files for ModelLoader (GMS and MX variants) are updated to introduce a shared _SOURCE_IDENTITY stub, monkeypatch SourceIdentity.from_model_config during loader construction, and extend checkpoint_loader.load_weights call assertions to verify the source_identity keyword argument is passed correctly.

Changes

source_identity plumbing in ModelLoader tests

Layer / File(s)	Summary
GMS test: _SOURCE_IDENTITY fixture, loader wiring, and load_weights assertion tests/unittest/_torch/pyexecutor/test_model_loader_gms.py	Adds a module-level _SOURCE_IDENTITY constant, patches SourceIdentity.from_model_config in _make_loader, wires backend.get_source_identity() to return it, and updates the RW-branch load_weights assertion to include source_identity=loader._source_identity.
MX test: _SOURCE_IDENTITY fixture, loader wiring, and load_weights assertion tests/unittest/_torch/pyexecutor/test_model_loader_mx.py	Introduces a parallel _SOURCE_IDENTITY stub with fixed fingerprints, patches SourceIdentity.from_model_config in _make_loader, and extends the MX success test to assert load_weights receives source_identity=loader._source_identity.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Possibly related PRs

• NVIDIA/TensorRT-LLM#14878: Directly introduces the SourceIdentity gate feature that this PR's test changes mock and assert against, including the source_identity parameter passed into checkpoint_loader.load_weights.

Suggested reviewers

• pcastonguay
• brb-nv
• galletas1712
• Funatiq
• symphonylyh

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: fixing stale MX/GMS ModelLoader test fixtures, using proper NVBugs reference format and [fix] type.
Description check	✅ Passed	The PR description adequately explains the issue, root cause, and solution. Test coverage section lists verification steps performed. PR Checklist is incomplete but not required for this fix-focused change.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

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[tensorrt-cicd]

PR_Github #55068 [ run ] completed with state SUCCESS. Commit: 5ec5c41
/LLM/main/L0_MergeRequest_PR pipeline #44055 completed with status: 'SUCCESS'

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