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diff --git a/testing/web-platform/tests/css/css-anchor-position/at-position-try-parse.html b/testing/web-platform/tests/css/css-anchor-position/at-position-try-parse.html
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+++ b/testing/web-platform/tests/css/css-anchor-position/at-position-try-parse.html
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+<!DOCTYPE html>
+<title>CSS Anchor Positioning Test: parsing of @position-try rules</title>
+<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#fallback-rule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/support/parsing-testcommon.js"></script>
+<script>
+test_valid_rule('@position-try --foo { }');
+test_valid_rule(`@position-try --foo { top: 1px; }`);
+
+// @position-try needs exactly one <dashed-ident> as its name
+test_invalid_rule('@position-try { }');
+test_invalid_rule('@position-try foo { }');
+test_invalid_rule('@position-try --foo --bar { }');
+test_invalid_rule('@position-try --foo, --bar { }');
+
+// @position-try only accepts a limited set of properties.
+test_valid_rule('@position-try --foo { backround-color: green; }',
+                '@position-try --foo { }');
+
+// @position-try accepts only regular style declarations. Other
+// contents should be ignored.
+test_valid_rule('@position-try --foo { @keyframes bar {} }',
+                '@position-try --foo { }');
+test_valid_rule('@position-try --foo { @font-face {} }',
+                '@position-try --foo { }');
+test_valid_rule('@position-try --foo { @media print {} }',
+                '@position-try --foo { }');
+test_valid_rule('@position-try --foo { & {} }',
+                '@position-try --foo { }');
+test_valid_rule('@position-try --foo { arbitrary garbage }',
+                '@position-try --foo { }');
+
+</script>