chromium/third_party/blink/web_tests/animations/custom-properties/angle-type-interpolation.html

<!DOCTYPE html>
<meta charset="UTF-8">
<style>
.parent {
  --angle: 30deg;
}
.target {
  --angle: 10deg;
}
</style>
<body>
<script src="../interpolation/resources/interpolation-test.js"></script>
<script>
CSS.registerProperty({
  name: '--angle',
  syntax: '<angle>',
  initialValue: '40deg',
  inherits: false,
});

assertInterpolation({
  property: '--angle',
  from: neutralKeyframe,
  to: '20deg',
}, [
  {at: -0.3, is: '7deg'},
  {at: 0, is: '10deg'},
  {at: 0.5, is: '15deg'},
  {at: 1, is: '20deg'},
  {at: 1.5, is: '25deg'},
]);

assertInterpolation({
  property: '--angle',
  from: 'initial',
  to: '20deg',
}, [
  {at: -0.3, is: '46deg'},
  {at: 0, is: '40deg'},
  {at: 0.5, is: '30deg'},
  {at: 1, is: '20deg'},
  {at: 1.5, is: '10deg'},
]);

assertInterpolation({
  property: '--angle',
  from: 'inherit',
  to: '20deg',
}, [
  {at: -0.3, is: '33deg'},
  {at: 0, is: '30deg'},
  {at: 0.5, is: '25deg'},
  {at: 1, is: '20deg'},
  {at: 1.5, is: '15deg'},
]);

assertInterpolation({
  property: '--angle',
  from: 'unset',
  to: '20deg',
}, [
  {at: -0.3, is: '46deg'},
  {at: 0, is: '40deg'},
  {at: 0.5, is: '30deg'},
  {at: 1, is: '20deg'},
  {at: 1.5, is: '10deg'},
]);

assertInterpolation({
  property: '--angle',
  from: '-10deg',
  to: '10deg',
}, [
  {at: -0.3, is: '-16deg'},
  {at: 0, is: '-10deg'},
  {at: 0.5, is: '0deg'},
  {at: 1, is: '10deg'},
  {at: 1.5, is: '20deg'},
]);

assertInterpolation({
  property: '--angle',
  from: '10rad',
  to: '20rad',
}, [
  {at: -0.3, is: '401.07deg'},
  {at: 0, is: '572.958deg'},
  {at: 0.5, is: '859.437deg'},
  {at: 1, is: '1145.92deg'},
  {at: 1.5, is: '1432.39deg'},
]);

assertInterpolation({
  property: '--angle',
  from: '200grad',
  to: '90deg',
}, [
  {at: -0.3, is: '207deg'},
  {at: 0, is: '180deg'},
  {at: 0.5, is: '135deg'},
  {at: 1, is: '90deg'},
  {at: 1.5, is: '45deg'},
]);
</script>
</body>