aria-level tests for headingoffset #203
Description
The new "Heading Levels & Offsets" HTML specification allows computing a heading offset based on ancestors (https://html.spec.whatwg.org/multipage/sections.html#heading-levels-&-offsets).
We should ensure that:
- Accessible nodes provide the aria level with the computed offset, for testing.
- We have tests written which exercise the various levels.
We have a fairly comprehensive test suite for levels https://github.com/web-platform-tests/wpt/blob/master/html/semantics/sections/headingoffset-and-headingreset.html which uses the :heading(n) pseudo to determine matches. This should be straightforward to port this document and refactor the tests to assert the aria level matches what is expected.