<!DOCTYPE html> <html class="reftest-wait"> <style> #target { animation: red 100s; } @keyframes red { 0% { background-color: red; } 100% { background-color: red; } } div { background-color: green; width: 100px; height: 100px; } </style> <div id="target"></div> <script> document.addEventListener('MozReftestInvalidate', () => { requestAnimationFrame(() => { document.styleSheets[0].cssRules[0].style.animationName = 'non-existent'; document.documentElement.classList.remove('reftest-wait'); }); }, false); </script>