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+<!DOCTYPE html>
+<title>Tests basics of the 'position-fallback' property</title>
+<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#propdef-position-fallback">
+<link rel="author" href="mailto:xiaochengh@chromium.org">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/support/parsing-testcommon.js"></script>
+<script src="/css/support/computed-testcommon.js"></script>
+<script src="/css/support/inheritance-testcommon.js"></script>
+<script src="/css/support/interpolation-testcommon.js"></script>
+
+<div id="container">
+  <div id="target"></div>
+</div>
+
+<script>
+// position-fallback: none | <dashed-ident>
+test_valid_value('position-fallback', 'none');
+test_valid_value('position-fallback', '--foo');
+test_invalid_value('position-fallback', 'foo-bar');
+test_invalid_value('position-fallback', '--foo --bar')
+test_invalid_value('position-fallback', '--foo, --bar')
+test_invalid_value('position-fallback', '100px');
+test_invalid_value('position-fallback', '100%');
+
+// Computed value: as specified
+test_computed_value('position-fallback', 'none');
+test_computed_value('position-fallback', '--foo');
+
+// Initial: none
+// Inherited: no
+assert_not_inherited('position-fallback', 'none', '--foo');
+
+// Animation type: discrete
+test_no_interpolation({
+  property: 'position-fallback',
+  from: '--foo',
+  to: 'none',
+});
+</script>