lib/jsdom/living/helpers/shadow-dom.js
function signalSlotChange(slot) {
  if (!signalSlotList.some(entry => entry === slot)) {
    signalSlotList.push(slot);
  }

  queueMutationObserverMicrotask();
}
function signalSlotChange(slot) {
  if (!signalSlotList.some(entry => entry === slot)) {
    signalSlotList.push(slot);
  }

  queueMutationObserverMicrotask();
}
https://dom.spec.whatwg.org/#signal-a-slot-change