Many VR UI scene tests manipulate the model and verify resulting element visibilty.  For animated elements, this requires advancing time to let animations either start or complete.

The animation aspect is relatively separate from the notion of whether an element will become visible/invisible in the future.

To improve ease of testing, we should implement a GetTargetVisibility variant that walks the tree and determines the true future visibility of an element.  Unit test IsVisible helpers would switch to use this, and time-advancing would no longer be necessary in most tests.