We do have https://webvr.info/samples/test-canvas-attributes.html , but that seems to mainly check that the attributes don't break rendering, it's a bit unobvious and sometimes subtle what the expected result should look like. Also, it's missing preserveDrawingBuffer=true, and that should specifically do incremental drawing without clearing.

Is the goal to verify the paths don't fail or that the graphics look correct? If the former, would this be a good Web Platform Test? Would it be useful even if some implementations mock the VR device path?

Marking as assigned to myself, but if someone else has time to do this before me, they are welcome to it.

The goal is to verify that the paths don't fail, and that the graphics look correct - things like preserved drawing buffers should actually render correctly.

Removing Blink>WebVR component and assigning to Blink>WebXR 

Removing Blink>WebVR component and assigning to Blink>WebXR