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diff --git a/testing/web-platform/tests/css/css-anchor-position/inset-area-function.html b/testing/web-platform/tests/css/css-anchor-position/inset-area-function.html
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+++ b/testing/web-platform/tests/css/css-anchor-position/inset-area-function.html
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+<!DOCTYPE html>
+<title>CSS Anchor Positioning: inset-area()</title>
+<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#position-try-options">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+  #cb {
+    position: relative;
+    width: 200px;
+    height: 200px;
+    border: 1px solid black;
+  }
+  #anchor {
+    position: absolute;
+    left: 100px;
+    top: 100px;
+    width: 80px;
+    height: 80px;
+    background-color: tomato;
+    anchor-name: --a;
+  }
+  #target, #ref {
+    position: absolute;
+    width: 40px;
+    height: 40px;
+    background-color: skyblue;
+    inset-area: bottom right;
+    position-anchor: --a;
+  }
+  #ref {
+    background-color: seagreen;
+  }
+</style>
+<style id=style>
+</style>
+<div id=cb>
+  <div id=anchor></div>
+  <div id=target></div>
+  <div id=ref></div>
+</div>
+<script>
+
+// Test that a given inset-area() produces the same result as a reference
+// element that is styled with an inset-area declaration directly.
+function test_inset_area_fn(inset_area_function, inset_area_expected) {
+  test((t) => {
+    t.add_cleanup(() => {
+      style.textContent = '';
+    });
+    style.textContent = `
+      #target {
+        position-try-options: ${inset_area_function};
+      }
+      #ref {
+        inset-area: ${inset_area_expected};
+      }
+    `;
+    assert_equals(target.offsetLeft, ref.offsetLeft, 'offsetLeft');
+    assert_equals(target.offsetTop, ref.offsetTop, 'offsetTop');
+  }, `${inset_area_function}, ${inset_area_expected}`);
+}
+
+test_inset_area_fn('inset-area(top left)', 'top left');
+test_inset_area_fn('inset-area(span-top left)', 'span-top left');
+test_inset_area_fn('inset-area(top span-left)', 'top span-left');
+test_inset_area_fn('inset-area(top center)', 'top center');
+test_inset_area_fn('inset-area(left center)', 'left center');
+test_inset_area_fn('inset-area(start center)', 'start center');
+test_inset_area_fn('inset-area(center start)', 'center start');
+
+</script>