chromium/third_party/blink/web_tests/animations/cross-fade-background-image.html

<html>
<head>
  <style>
    #box {
        position: absolute;
        left: 100px;
        top: 100px;
        height: 100px;
        width: 100px;
        background-color: red;
    }
    #boxShorthand {
        position: absolute;
        left: 100px;
        top: 200px;
        height: 100px;
        width: 100px;
        background-color: red;
    }
    #boxStatic {
        position: absolute;
        left: 100px;
        top: 300px;
        height: 100px;
        width: 100px;
        background-color: red;
        background-image: cross-fade(50% url(resources/blue-100.png), url(resources/green-100.png));
    }
    @keyframes anim {
        from { background-image: url(resources/blue-100.png); }
        to   { background-image: url(resources/green-100.png); }
    }
    @keyframes animShorthand {
        from { background: url(resources/blue-100.png); }
        to   { background: url(resources/green-100.png); }
    }
  </style>
  <script src="resources/animation-test-helpers.js" type="text/javascript" charset="utf-8"></script>
  <script type="text/javascript" charset="utf-8">
    window.onload = () => {
      const animations = [
        { id: 'box', keyframes: 'anim' },
        { id: 'boxShorthand', keyframes: 'animShorthand' }
      ];
      const reference = 'boxStatic';
      const property = 'backgroundImage';
      const tolerance = 0.05;
      runAnimationMidpointTest(animations, reference, property, tolerance);
    };
  </script>
</head>
<body>
<div id="box"></div>
<div id="boxStatic"></div>
<div id="boxShorthand"></div>
<div id="result"></div>
</body>
</html>