chromium/third_party/blink/web_tests/animations/missing-keyframe-properties-repeating.html

<!DOCTYPE html>
<html>
<head>
  <style type="text/css" media="screen">
    #box1 {
      position: relative;
      height: 100px;
      width: 100px;
      left: 0;
      background-color: blue;
      margin: 0;
      animation-duration: 2s;
      animation-timing-function: linear;
      animation-iteration-count: 2;
      animation-direction: alternate;
      animation-name: move;
    }
    @keyframes move {
        from {
          opacity: 1;
        }
        50% {
          opacity: 1;
          left: 100px;
        }
        to {
          opacity: 1;
        }
    }
    
    /* Test reversing animation with missing values */

  </style>
  <script src="resources/animation-test-helpers.js" type="text/javascript" charset="utf-8"></script>
  <script type="text/javascript" charset="utf-8">
    
    const expectedValues = [
      // [time, element-id, property, expected-value, tolerance]
      [1, "box1", "left", 100, 15],
      [2, "box1", "left", 0, 15],
      [3, "box1", "left", 100, 15],
    ];
    
    runAnimationTest(expectedValues);
  </script>
</head>
<body>
<div id="box1"></div>
<div id="result">
</div>
</body>
</html>