This is a testharness.js-based test.
FAIL Focus should jump to fallback elements when a slot does not have any assigned nodes. assert_equals: Focus should move forward from x-foo/j2 to x-foo/k1 expected Element node <input id="k1" tabindex="1" value="k1"></input> but got Element node <input id="i0" tabindex="0" value="i0"></input>
Harness: the test ran to completion.

