test_spacecraftHubOnlyFastPath

Unit tests for the automatic hub-only spacecraft dynamics fast path.

When no state effectors are attached and point \(B\) is colocated with the hub center of mass, Spacecraft can bypass the general Backsubstitution matrix assembly and ask HubEffector to compute direct rigid-body derivatives. These tests validate the resulting dynamics against an analytic case and verify that inertia changes refresh the cached factorization.

test_spacecraftHubOnlyFastPath.test_hub_only_inertia_cache_refreshes(update_mode)

Use current effective inertia after direct updates, configuration changes, and resets.

test_spacecraftHubOnlyFastPath.test_spacecraftHubOnlyFastPath_matchesAnalyticForceTorque()

Hub-only fast path must reproduce direct rigid-body force/torque motion.