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diff --git a/testing/web-platform/tests/css/css-ui/animation/outline-offset-composition.html b/testing/web-platform/tests/css/css-ui/animation/outline-offset-composition.html
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index 0000000000..984a63fdc3
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+++ b/testing/web-platform/tests/css/css-ui/animation/outline-offset-composition.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<title>outline-offset composition</title>
+<link rel="help" href="https://drafts.csswg.org/css-ui-3/#outline-offset">
+<meta name="assert" content="outline-offset supports animation by computed value">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/support/interpolation-testcommon.js"></script>
+
+<body>
+<script>
+test_composition({
+  property: 'outline-offset',
+  underlying: '50px',
+  addFrom: '100px',
+  addTo: '200px',
+}, [
+  {at: -0.3, expect: '120px'},
+  {at: 0, expect: '150px'},
+  {at: 0.5, expect: '200px'},
+  {at: 1, expect: '250px'},
+  {at: 1.5, expect: '300px'},
+]);
+
+test_composition({
+  property: 'outline-offset',
+  underlying: '100px',
+  addFrom: '10px',
+  addTo: '2px',
+}, [
+  {at: -0.5, expect: '114px'},
+  {at: 0, expect: '110px'},
+  {at: 0.5, expect: '106px'},
+  {at: 1, expect: '102px'},
+  {at: 1.5, expect: '98px'},
+]);
+
+test_composition({
+  property: 'outline-offset',
+  underlying: '10em',
+  addFrom: '100px',
+  addTo: '20em',
+}, [
+  {at: -0.3, expect: 'calc(130px + 4em)'},
+  {at: 0, expect: 'calc(100px + 10em)'},
+  {at: 0.5, expect: 'calc(50px + 20em)'},
+  {at: 1, expect: '30em'},
+  {at: 1.5, expect: 'calc(-50px + 40em)'},
+]);
+
+test_composition({
+  property: 'outline-offset',
+  underlying: '50px',
+  addFrom: '100px',
+  replaceTo: '200px',
+}, [
+  {at: -0.3, expect: '135px'},
+  {at: 0, expect: '150px'},
+  {at: 0.5, expect: '175px'},
+  {at: 1, expect: '200px'},
+  {at: 1.5, expect: '225px'},
+]);
+</script>
+</body>