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<head>
<title>Custom Elements: document.implementation.createElement must not instantiate a custom element</title>
<meta name="author" title="Ryosuke Niwa" href="mailto:rniwa@webkit.org">
<meta name="assert" content="document.implementation.createElement must not instantiate a custom element">
<link rel="help" content="https://dom.spec.whatwg.org/#dom-domimplementation-createdocument">
<link rel="help" content="https://html.spec.whatwg.org/#look-up-a-custom-element-definition">
<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<script src="../../imported/w3c/web-platform-tests/custom-elements/resources/custom-elements-helpers.js"></script>
</head>
<body>
<div id="log"></div>
<script>

const xhtmlNamespaceURI = 'http://www.w3.org/1999/xhtml';

test_with_window((contentWindow, contentDocument) => {
    let constructorCount = 0;
    class MyCustomElement extends contentWindow.HTMLElement {
        constructor() {
            super();
            constructorCount++;
        }
    }
    contentWindow.customElements.define('my-custom-element', MyCustomElement);
    const instance = contentDocument.createElement('my-custom-element');
    assert_true(instance instanceof MyCustomElement);
    assert_equals(constructorCount, 1);

    const newDocument = contentDocument.implementation.createDocument(xhtmlNamespaceURI, 'my-custom-element', null);
    assert_equals(constructorCount, 1);
    assert_true(newDocument.documentElement instanceof contentWindow.HTMLElement);
    assert_equals(newDocument.documentElement.localName, 'my-custom-element');
    assert_false(newDocument.documentElement instanceof MyCustomElement);
}, 'document.createElement invoke a custom element constructor with no arguments');

</script>
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