LayoutTests/animations/top-left-percent-interpolation.html

<style>
#container {
  border: 2px solid blue;
  width:200px;
  height:200px;
  position:relative;
}

#box1 {
  position: absolute;
  top: 0;
  left: 0;
  width: 100px;
  height: 100px;
  background: blue;

  animation: top-left 1s linear;
}

#box2 {
  position: absolute;
  bottom: 0;
  right: 0;
  width: 100px;
  height: 100px;
  background: green;

  animation: bottom-right 1s linear;
}

@keyframes top-left {
  100% {
     top: 100%;
     left: 100%;
  }
}
@keyframes bottom-right {
  100% {
     bottom: 100%;
     right: 100%;
  }
}
</style>
<script src="resources/animation-test-helpers.js"></script>
<script>

const expectedValues = [
    // [animation-name, time, element-id, property, expected-value, tolerance]
    ["top-left", 0.5, "box1", "left", 100, 20],
    ["top-left", 0.5, "box1", "top", 100, 20],
    ["bottom-right", 0.5, "box2", "right", 100, 20],
    ["bottom-right", 0.5, "box2", "bottom", 100, 20],
];

runAnimationTest(expectedValues);
</script>
<div id="container">
  <div id="box1"></div>
  <div id="box2"></div>
</div>
<div id="result">
</div>