effect-value-interval-distance.html

<!doctype html>
<meta charset=utf-8>
<title>The effect value of a keyframe effect: Calculating the interval
  distance between keyframes</title>
<link rel="help" href="https://drafts.csswg.org/web-animations/#the-effect-value-of-a-keyframe-animation-effect">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../../testcommon.js"></script>
<body>
<div id="log"></div>
<script>
'use strict';

test(t => {
  // In Firefox there was a floating precision bug in the calculation of the
  // progress at the end of the 0.2<->1.0 interval. This test exercises that
  // calculation in case other UAs suffer from the same problem.
  const target = createDiv(t);
  const anim = target.animate(
    [
      { opacity: 0 },
      { offset: 0.2, opacity: 1, easing: 'step-end' },
      { opacity: 0 },
    ],
    {
      duration: 1000,
      fill: 'forwards',
    }
  );

  anim.currentTime = 1000;
  assert_equals(getComputedStyle(target).opacity, '0');
}, 'Interval distance is calculated correctly (precision test)');

</script>
</body>

chromium/third_party/blink/web_tests/external/wpt/web-animations/animation-model/keyframe-effects/effect-value-interval-distance.html