Articulation Reordering Part 5/8: Extract articulation interface test utilities

[AntoineRichard]

Description

Moves the articulation interface test factories into a shared utility module mirroring Part 1's rigid object extraction, with ordering-aware construction hooks used by Part 7's cross-backend suite.

Part 5/8 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: 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 (this PR): 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

Note

All parts target develop, so until the preceding parts merge this PR's diff includes them. The true delta of this part is this compare.

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_articulation_iface.py -> 4086 passed, 96 skipped, 32 xfailed (with Newton and PhysX wired, OVPhysX not yet — exercises the unwired-backend identity path)
• ./isaaclab.sh -f -> all hooks pass

[ooctipus]

Agent review: the Part 4 (#6337) review pointed the duplicated actuator ordering-trace machinery (test_newton_actuators_{newton,physx}.py, ~107 identical lines) at this part's shared utilities — but this module can't host it as designed: it's directory-local (resolved only via pytest's per-directory sys.path; the Newton/PhysX test dirs can't import it), and importing it boots Kit and monkeypatches PhysxManager.get_physics_sim_view module-wide, so a real-simulation test file can't pull in just the torch-based trace helpers. The installable isaaclab.test package (already imported cross-package by sibling backend tests, e.g. isaaclab.test.utils) is a home that would work — worth settling here so the Part 4 consolidation lands somewhere it can live.

[AntoineRichard]

Added a pure installable helper at isaaclab.test.utils.articulation_ordering. Both Newton and PhysX actuator tests now import the same canonicalization and trace assertion directly; the backend factories remain directory-local, and the helper is not eagerly re-exported from isaaclab.test.utils.

[ooctipus]

Agent review: this kitless-detection/AppLauncher/omni-stub/gravity-mock preamble is the third verbatim copy in this directory (after Part 1's two _rigid_object*_iface_test_utils.py), ~150 duplicated lines total, and the copies have already drifted in comment wording. It's load-bearing CI plumbing — the LD_PRELOAD signature check and the stub list must stay in lockstep across all copies for the kitless runner — and the extraction needs zero parameters (e.g. from _iface_test_boot import simulation_app at the top of all three).

[AntoineRichard]

Extracted the shared Kit/kitless setup into _iface_test_boot.py and switched all three interface utility modules to import its simulation_app. A subprocess regression verifies that they resolve the same bootstrap object.

[ooctipus]

Agent review: this unconditional isaaclab_physx import defeats the find_spec("isaaclab_physx") guard ten lines below — if the package is genuinely optional the import needs to move under the guard; if it isn't, the guard can go.

[AntoineRichard]

Moved the PhysxManager import and gravity mock under the availability guard in all three interface utility modules. A subprocess regression blocks isaaclab_physx imports and verifies that the mock-only utilities still load.

[greptile-apps]

Greptile Summary

This PR extracts articulation backend factory functions from test_articulation_iface.py into a new shared module _articulation_iface_test_utils.py, mirroring the rigid-object extraction done in Part 1 and adding ordering-aware construction hooks (joint_ordering, body_ordering, is_fixed_base) needed by Part 7's cross-backend suite.

• The new utility adds _resolve_and_install_ordering_maps() / _ordering_configure_backend_staging() call sequences into each factory, and switches the Newton mock model's DOF count to account for floating-base DOFs (num_joints + 6 when is_fixed_base=False).
• Backend availability detection changes from try/except ImportError to importlib.util.find_spec, which no longer catches import failures for packages that exist on disk but have broken dependencies; isaaclab_physx is also imported unconditionally at module level, so any environment without it will fail to load the utility module entirely.
• The \"mock\" branch of get_articulation silently drops is_fixed_base, joint_ordering, and body_ordering, which can cause silent mismatches in Part 7's cross-backend ordering comparisons.

Confidence Score: 3/5

The test file itself is safe, but the new shared utility module has three issues that can break test runs in certain environments.

The utility module unconditionally imports isaaclab_physx at module level and replaces graceful try/except ImportError backend detection with bare find_spec guards, meaning any environment where a backend package is discoverable but not importable will crash the entire session. The mock backend also silently discards joint_ordering and body_ordering params that Part 7 will pass.

_articulation_iface_test_utils.py — the unconditional physx import block (lines 57-59), the find_spec backend guards (lines 67-98), and the mock branch in get_articulation (lines 546-558) all need attention.

Important Files Changed

Filename	Overview
source/isaaclab/test/assets/_articulation_iface_test_utils.py	New shared utility module extracting articulation factory functions; switches backend detection from try/except to find_spec (dropping graceful ImportError handling), unconditionally imports isaaclab_physx at module level, and silently drops ordering params for the mock backend.
source/isaaclab/test/assets/test_articulation_iface.py	Removes all factory/setup boilerplate, delegating to the new utility module; adds one new PhysX-only identity-ordering proxy-array reuse test; minor comment block relocation.
source/isaaclab/changelog.d/articulation-reordering-p5.skip	Empty skip-file marker for the changelog tooling; no code changes.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant T as test_articulation_iface.py
    participant U as _articulation_iface_test_utils.py
    participant P as isaaclab_physx (unconditional import)
    participant N as isaaclab_newton (find_spec guarded)
    participant O as isaaclab_ovphysx (find_spec guarded)
    participant M as MockArticulation

    T->>U: import BACKENDS, get_articulation
    U->>P: from isaaclab_physx.physics import PhysxManager (unconditional)
    U->>P: "SimulationManager.get_physics_sim_view = MagicMock(...)"
    U->>N: importlib.util.find_spec(isaaclab_newton)
    U->>O: importlib.util.find_spec(isaaclab_ovphysx)

    T->>T: "@pytest.fixture articulation_iface(request)"
    T->>U: get_articulation(backend, ...)
    alt "backend == physx"
        U->>U: create_physx_articulation(...)
        U->>U: _resolve_and_install_ordering_maps()
        U->>U: _ordering_configure_backend_staging()
    else "backend == newton"
        U->>U: create_newton_articulation(...)
        U->>U: _resolve_and_install_ordering_maps()
        U->>U: _ordering_configure_backend_staging()
    else "backend == ovphysx"
        U->>U: create_ovphysx_articulation(...)
        U->>U: _resolve_and_install_ordering_maps()
        U->>U: _create_buffers()
    else "backend == mock"
        U->>M: MockArticulation(...) [ordering params ignored]
    end
    U-->>T: (articulation, view)

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sequenceDiagram
    participant T as test_articulation_iface.py
    participant U as _articulation_iface_test_utils.py
    participant P as isaaclab_physx (unconditional import)
    participant N as isaaclab_newton (find_spec guarded)
    participant O as isaaclab_ovphysx (find_spec guarded)
    participant M as MockArticulation

    T->>U: import BACKENDS, get_articulation
    U->>P: from isaaclab_physx.physics import PhysxManager (unconditional)
    U->>P: "SimulationManager.get_physics_sim_view = MagicMock(...)"
    U->>N: importlib.util.find_spec(isaaclab_newton)
    U->>O: importlib.util.find_spec(isaaclab_ovphysx)

    T->>T: "@pytest.fixture articulation_iface(request)"
    T->>U: get_articulation(backend, ...)
    alt "backend == physx"
        U->>U: create_physx_articulation(...)
        U->>U: _resolve_and_install_ordering_maps()
        U->>U: _ordering_configure_backend_staging()
    else "backend == newton"
        U->>U: create_newton_articulation(...)
        U->>U: _resolve_and_install_ordering_maps()
        U->>U: _ordering_configure_backend_staging()
    else "backend == ovphysx"
        U->>U: create_ovphysx_articulation(...)
        U->>U: _resolve_and_install_ordering_maps()
        U->>U: _create_buffers()
    else "backend == mock"
        U->>M: MockArticulation(...) [ordering params ignored]
    end
    U-->>T: (articulation, view)

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Comments Outside Diff (1)

1. source/isaaclab/test/assets/_articulation_iface_test_utils.py, line 546-558 (link)

   Ordering params silently dropped for mock backend

   get_articulation accepts is_fixed_base, joint_ordering, and body_ordering, but create_mock_articulation takes none of them — so any caller passing these for the "mock" backend silently receives a vanilla, unordered instance. Part 7's cross-backend ordering suite is expected to drive get_articulation with explicit orderings for all backends. If the mock path doesn't honour those params, any cross-backend assertion comparing mock output to physx/newton output under a non-identity ordering will produce a misleading pass or a confusing mismatch.

_{Reviews (1): Last reviewed commit: "Adapt iface test utilities to reworked o..." | Re-trigger Greptile}

[greptile-apps]

Unconditional isaaclab_physx import

isaaclab_physx is imported and patched at module level, outside any availability guard. If isaaclab_physx is absent (e.g., a pure Newton or mock-only environment), importing _articulation_iface_test_utils will raise ImportError before any test can run — including the mock-backend tests that are supposed to "always be available". The old test file had the same issue, but moving to a shared utility that other files will also import makes the blast radius larger.

[AntoineRichard]

Fixed across all three interface utility modules: PhysxManager and its gravity mock now live inside the isaaclab_physx availability guard. The new mock-only subprocess regression explicitly rejects any attempted isaaclab_physx import.

[greptile-apps]

find_spec does not guard against import errors

The old code used try/except ImportError which gracefully degrades if a backend package exists on disk but fails to import (missing transitive dependency, broken extension, etc.). importlib.util.find_spec only checks whether the package is locatable; it does not attempt the import. If isaaclab_physx, isaaclab_newton, or isaaclab_ovphysx is on the PYTHONPATH but unimportable, the bare from … import … inside the if block will raise an unhandled ImportError at module load time, crashing the entire test session instead of gracefully skipping the backend. This is especially relevant for OvPhysX, which the PR description notes is not yet fully wired.

[AntoineRichard]

Keeping this behavior intentionally. find_spec treats an absent backend as unavailable, while a discoverable backend whose internal dependency is broken should fail loudly rather than silently reduce test coverage. Added a subprocess regression that distinguishes those two cases and requires the internal ModuleNotFoundError to propagate.

[greptile-apps]

The triple-quoted string here is a standalone expression, not a module/function docstring. Python evaluates it (creating a string object) but immediately discards it, so it produces no effect and will not appear in __doc__. Convert to a regular comment to express the intent clearly.

Suggested change

	"""
	Check which backends are available.
	"""
	# ---------------------------------------------------------------------------
	# Check which backends are available.
	# ---------------------------------------------------------------------------

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

[AntoineRichard]

Converted the discarded string expression to the regular section comment shown in the suggestion.

[AntoineRichard]

Greptile follow-up: the mock factory now preserves is_fixed_base. Because MockArticulation does not implement articulation ordering, explicit joint_ordering or body_ordering is rejected with a clear ValueError instead of being silently ignored; the new subprocess regression covers both behaviors.