This is a testharness.js-based test.
FAIL Test Document.createElement() creates custom element of type, specified by typeExtension argument assert_equals: Custom element type should be the type extension of the custom element expected object "[object HTMLElement]" but got object "[object HTMLElement]"
FAIL Test Document.createElementNS() creates custom element of type, specified by typeExtension argument assert_equals: Custom element type should be the type extension of the custom element expected object "[object HTMLElement]" but got object "[object HTMLElement]"
FAIL Test Document.createElement() creates custom element of type, specified by typeExtension argument. Definition for localName is absent assert_equals: Custom element type should be the type extension of the custom element expected object "[object HTMLElement]" but got object "[object HTMLElement]"
FAIL Test Document.createElementNS() creates custom element of type, specified by typeExtension argument. Definition for localName is absent assert_equals: Custom element type should be the type extension of the custom element expected object "[object HTMLElement]" but got object "[object HTMLElement]"
Harness: the test ran to completion.

