diff --git a/css/css-contain/content-visibility/content-visibility-with-top-layer-008.html b/css/css-contain/content-visibility/content-visibility-with-top-layer-008.html
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+<!doctype html>
+<meta charset="utf8">
+<title>CSS Content Visibility: Contentvisibilityautostatechange fires once when c-v auto's dialog ancestor show</title>
+<link rel="author" title="Cathie Chen" href="mailto:cathiechen@igalia.com">
+<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
+<meta name="assert" content="Contentvisibilityautostatechange fires once when c-v auto's dialog ancestor show">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/rendering-utils.js"></script>
+
+<style>
+#inner {
+    content-visibility: auto;
+    contain-intrinsic-size: 100px 100px;
+}
+</style>
+
+<dialog id="dialog">
+    <div id="inner">
+        <div style="height: 200px; width: 200px;">content</div>
+    </div>
+    <div id="spacer" style="height: 100000px;"></div>
+</dialog>
+
+<script>
+promise_test(async () => {
+    let count = 0;
+    inner.addEventListener("contentvisibilityautostatechange", (e) => {
+        count++;
+    });
+
+    dialog.show();
+    // getBoundingClientRect shouldn't trigger "contentvisibilityautostatechange", because the proximity to the viewport is not determined now.
+    inner.getBoundingClientRect().height;
+
+    // It takes at least one frame to determine the proximity to the viewport.
+    await waitForAtLeastOneFrame();
+    // getBoundingClientRect should trigger "contentvisibilityautostatechange" now.
+    inner.getBoundingClientRect().height;
+
+    await waitForAtLeastOneFrame();
+    assert_equals(count, 1);
+    dialog.close();
+}, "Contentvisibilityautostatechange fires once when c-v auto's dialog ancestor show()");
+</script>
