This is a testharness.js-based test.
[FAIL] HTMLAnchorElement interface: attribute attributionSourceId
  assert_true: The prototype object must have a property "attributionSourceId" expected true got false
[FAIL] HTMLAnchorElement interface: document.createElement("a") must inherit property "attributionSourceId" with the proper type
  assert_inherits: property "attributionSourceId" not found in prototype chain
Harness: the test ran to completion.