localName, 'my-custom-element');
    assert_equals(customElement.namespaceURI, 'http://www.w3.org/1999/xhtml', 'A custom element HTML must use HTML namespace');

}, 'HTML parser must NOT create a custom element before customElements.define is called');

customElements.define('my-custom-element', MyCustomElement);

</script>
<my-custom-element id="instance2"></my-custom-element>
<script>

test(function () {
    var customElement = document.getElementById('instance2');

    assert_true(customElement instanceo