Synthetische MutationObserver-Testumgebung für deterministisches DOM-Effekt-Testen

function createDOMMutationHarness(targetNode) {
  const recordLog = [];
  const observer = new MutationObserver((mutations) => {
    for (const mutation of mutations) {
      recordLog.push({ type: mutation.type, target: mutation.target.nodeName, addedCount: mutation.addedNodes.length });
    }
  });
  observer.observe(targetNode, { attributes: true, childList: true, subtree: true });
  return {
    getMutations: () => [...recordLog],
    disconnect: () => observer.disconnect()
  };
}