Articulation Reordering Part 1/8: Extract rigid object interface test utilities

[AntoineRichard]

Description

Moves the rigid object and rigid object collection interface test factories into shared underscore-prefixed utility modules so later parts can reuse them. Pure code movement with no behavior change and no ordering content.

Part 1/8 of the series splitting #6248 into independently reviewable units. #6248 remains open, untouched, as the reference implementation; this stack was cut from its final tree after a develop sync (Kamino Core, Newton bump, OVPhysX 0.5.1).

Stack

• Part 1/8 (this PR): Articulation Reordering Part 1/8: Extract rigid object interface test utilities #6334 — Extract rigid object interface test utilities
• Part 2/8: Articulation Reordering Part 2/8: Core ordering foundation #6335 — Core ordering foundation
• Part 3/8: Articulation Reordering Part 3/8: Newton backend #6336 — Newton backend
• Part 4/8: Articulation Reordering Part 4/8: PhysX backend #6337 — PhysX backend
• Part 5/8: Articulation Reordering Part 5/8: Extract articulation interface test utilities #6338 — Extract articulation interface test utilities
• Part 6/8: Articulation Reordering Part 6/8: OVPhysX backend #6339 — OVPhysX backend
• Part 7/8: Articulation Reordering Part 7/8: Cross-backend ordering interface tests #6340 — Cross-backend ordering interface tests
• Part 8/8: Articulation Reordering Part 8/8: Events, consumers, and documentation #6341 — Events, consumers, and documentation

Type of change

• Test/documentation/refactor change

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have added tests that prove my fix is effective or that my feature works
• I have added a changelog fragment under source/<pkg>/changelog.d/ for every touched package
• My name exists in CONTRIBUTORS.md

Test Plan

• ./isaaclab.sh -p -m pytest source/isaaclab/test/assets/test_rigid_object_iface.py -> 1478 passed, 12 xfailed
• ./isaaclab.sh -p -m pytest source/isaaclab/test/assets/test_rigid_object_collection_iface.py -> 1902 passed; the 7 failures + 636 errors are pre-existing on develop in the local environment (OVPhysX 0.4.13 wheel vs the 0.5.x binding API from Fetch OVPhysX wheelhouse CI through NGC + 0.5.1 bump #6314) — fail-set identical to the develop baseline
• ./isaaclab.sh -f -> all hooks pass

[greptile-apps]

Greptile Summary

This PR extracts the backend factory functions and simulator bootstrap logic from test_rigid_object_iface.py and test_rigid_object_collection_iface.py into two new underscore-prefixed utility modules (_rigid_object_iface_test_utils.py and _rigid_object_collection_iface_test_utils.py), so they can be reused by later parts of the articulation-reordering stack. The test files themselves are reduced to pure pytest logic, importing only BACKENDS and the dispatcher function from the new utilities.

• Two new utility modules are added containing all factory/mock-setup logic; the test files now delegate to them via a bare-name import that relies on pytest inserting the test/assets/ directory into sys.path.
• Backend detection is refactored from try/except ImportError blocks to importlib.util.find_spec() guards — a subtle behavioral change where a partially-installed backend (package findable but submodule import fails) would now raise at collection time instead of silently skipping that backend.
• import torch is carried into both utility files but is unused within them.

Confidence Score: 4/5

Safe to merge; the test logic itself is unchanged and all existing tests continue to pass.

The extraction is clean and the test bodies are untouched. The two utility files introduce a minor but real difference in how broken backend installs are handled (find_spec without a surrounding try/except), and carry an unused torch import — neither affects the passing test suite in practice, but they are worth cleaning up before the pattern is copy-pasted into Parts 5–8.

Both new utility files (_rigid_object_iface_test_utils.py and _rigid_object_collection_iface_test_utils.py) deserve a second look for the find_spec import-guard pattern and the unused torch import.

Important Files Changed

Filename	Overview
source/isaaclab/test/assets/_rigid_object_iface_test_utils.py	New utility module extracted from test_rigid_object_iface.py; uses importlib.util.find_spec() instead of try/except ImportError for backend detection, and imports torch without using it.
source/isaaclab/test/assets/_rigid_object_collection_iface_test_utils.py	New utility module extracted from test_rigid_object_collection_iface.py; same find_spec pattern change and unused torch import as the sibling utility file.
source/isaaclab/test/assets/test_rigid_object_iface.py	Factory functions and bootstrap removed; now imports BACKENDS and get_rigid_object from the new utility module. Test logic is unchanged.
source/isaaclab/test/assets/test_rigid_object_collection_iface.py	Factory functions and bootstrap removed; imports delegated to the new collection utility module. Test logic is unchanged.
source/isaaclab/changelog.d/articulation-reordering-p1.skip	Empty .skip file suppressing changelog requirement for this internal refactor PR.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    subgraph Before["Before (monolithic test files)"]
        TRI["test_rigid_object_iface.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object()\n- pytest tests"]
        TRCI["test_rigid_object_collection_iface.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object_collection()\n- pytest tests"]
    end
    subgraph After["After (extracted utilities)"]
        UTIL1["_rigid_object_iface_test_utils.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object()"]
        UTIL2["_rigid_object_collection_iface_test_utils.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object_collection()"]
        TRI2["test_rigid_object_iface.py\n- pytest tests only"]
        TRCI2["test_rigid_object_collection_iface.py\n- pytest tests only"]
        UTIL1 -->|imported by| TRI2
        UTIL2 -->|imported by| TRCI2
        UTIL1 -.->|future reuse| FUT["Part 5-8 articulation tests"]
        UTIL2 -.->|future reuse| FUT
    end

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flowchart TD
    subgraph Before["Before (monolithic test files)"]
        TRI["test_rigid_object_iface.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object()\n- pytest tests"]
        TRCI["test_rigid_object_collection_iface.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object_collection()\n- pytest tests"]
    end
    subgraph After["After (extracted utilities)"]
        UTIL1["_rigid_object_iface_test_utils.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object()"]
        UTIL2["_rigid_object_collection_iface_test_utils.py\n- _kitless / AppLauncher init\n- BACKENDS detection\n- create_*() factories\n- get_rigid_object_collection()"]
        TRI2["test_rigid_object_iface.py\n- pytest tests only"]
        TRCI2["test_rigid_object_collection_iface.py\n- pytest tests only"]
        UTIL1 -->|imported by| TRI2
        UTIL2 -->|imported by| TRCI2
        UTIL1 -.->|future reuse| FUT["Part 5-8 articulation tests"]
        UTIL2 -.->|future reuse| FUT
    end

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Comments Outside Diff (1)

1. source/isaaclab/test/assets/_rigid_object_iface_test_utils.py, line 403-415 (link)

   find_spec without import-level exception handling changes error semantics

   The original test files used try/except ImportError (and AttributeError for ovphysx) around each backend import block, so a partially-broken install would silently skip that backend. The utility files replace this with if importlib.util.find_spec("isaaclab_physx") is not None: — but the naked import inside the if block has no exception handler. If the package is discoverable but a specific submodule fails to load (e.g. a missing C extension in isaaclab_physx.assets.rigid_object.rigid_object), the exception now propagates to the top level and kills the entire test module at collection time rather than just omitting that backend. The same pattern is repeated for the newton and ovphysx blocks, and in _rigid_object_collection_iface_test_utils.py. The original except (ImportError, AttributeError) guard for the ovphysx block is also missing here.

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