fieldset-elements-after-upgrade.html

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This WPT test may be referenced by the following Test IDs:
- /custom-elements/form-associated/fieldset-elements-after-upgrade.html - WPT Dashboard Interop Dashboard

<!doctype html>

<title>fieldset.elements is updated when a form-associated custom element upgrades</title>

<link rel="help" href="https://html.spec.whatwg.org/#dom-fieldset-elements">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<fieldset id="outer">

  <fieldset id="inner">

    <legend><x-bar></x-bar></legend>

    <x-bar></x-bar>

  </fieldset>

</fieldset>

<script>

test(() => {

  const outer = document.getElementById("outer");

  const inner = document.getElementById("inner");

  assert_equals(outer.elements.length, 1, "outer before upgrade");

  assert_equals(inner.elements.length, 0, "inner before upgrade");

  customElements.define("x-bar", class extends HTMLElement {

    static formAssociated = true;

});

  assert_equals(outer.elements.length, 3, "outer after upgrade");

  assert_equals(inner.elements.length, 2, "inner after upgrade");

}, "Upgrading form-associated custom elements updates all ancestor fieldsets, including inside legend");

</script>