web-animations/responsive/borderRadius.html

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id='element'></div>
<script>

var element = document.getElementById('element');

test(function() {
    var keyframes = [
        {borderTopLeftRadius: '8% 16%'},
        {borderTopLeftRadius: '12% 24%'}
    ];

    element.style.width = '100';
    element.style.height = '200';
    var player = element.animate(keyframes, 10);
    player.pause();
    player.currentTime = 5;
    element.style.width = '300';
    element.style.height = '600';
    assert_equals(getComputedStyle(element).borderTopLeftRadius, '10% 20%');
}, 'Border radius percentages are supported');

test(function() {
    var keyframes = [
        {borderTopLeftRadius: '8em 16em'},
        {borderTopLeftRadius: '12em 24em'}
    ];

    element.style.fontSize = '10px';
    var player = element.animate(keyframes, 10);
    player.pause();
    player.currentTime = 5;
    element.style.fontSize = '20px';
    assert_equals(getComputedStyle(element).borderTopLeftRadius, '200px 400px');
}, 'Border radius lengths respond to style changes');

</script>