1 files changed, 58 insertions, 0 deletions
diff --git a/testing/web-platform/tests/css/css-cascade/at-scope-parsing.html b/testing/web-platform/tests/css/css-cascade/at-scope-parsing.html
new file mode 100644
index 0000000000..13fe94fe89
--- /dev/null
+++ b/testing/web-platform/tests/css/css-cascade/at-scope-parsing.html
@@ -0,0 +1,58 @@
+<!doctype html>
+<title>@scope: parsing</title>
+<link rel="help" href="https://drafts.csswg.org/css-cascade-6/#scope-atrule">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<main id=main></main>
+<script>
+  function test_valid(actual, expected) {
+    if (expected === undefined)
+      expected = actual;
+    test(t => {
+      t.add_cleanup(() => main.replaceChildren());
+      let style = document.createElement('style');
+      style.textContent = `${actual}{}`;
+      main.append(style);
+      assert_equals(style.sheet.rules.length, 1);
+      let rule = style.sheet.rules[0];
+      assert_equals(rule.cssText, `${expected} {\n}`);
+    }, `${actual} is valid`);
+  }
+
+  function test_invalid(actual) {
+    test(t => {
+      t.add_cleanup(() => main.replaceChildren());
+      let style = document.createElement('style');
+      style.textContent = `${actual}{}`;
+      main.append(style);
+      assert_equals(style.sheet.rules.length, 0);
+    }, `${actual} is not valid`);
+  }
+
+  test_valid('@scope (.a)');
+  test_valid('@scope (.a + .b)');
+  test_valid('@scope (.a:hover)');
+  test_valid('@scope (.a:hover, #b, div)');
+  test_valid('@scope (:is(div, span))');
+
+  test_valid('@scope (.a) to (.b)');
+  test_valid('@scope (.a)to (.b)', '@scope (.a) to (.b)');
+  test_valid('@scope (.a) to (.b:hover, #c, div)');
+
+  // Forgiving behavior:
+  test_valid('@scope (.c <> .d)', '@scope ()');
+  test_valid('@scope (.a, .c <> .d)', '@scope (.a)');
+  test_valid('@scope (.a <> .b, .c)', '@scope (.c)');
+  test_valid('@scope (div::before)', '@scope ()');
+  test_valid('@scope (div::after)', '@scope ()');
+  test_valid('@scope (slotted(div))', '@scope ()');
+  test_valid('@scope (.a) to (div::before)', '@scope (.a) to ()');
+
+  test_invalid('@scope (.a) unknown (.c)');
+  test_invalid('@scope (.a) to unknown (.c)');
+  test_invalid('@scope (.a) 1px (.c)');
+  test_invalid('@scope (.a) to unknown(c)');
+  test_invalid('@scope unknown(.a)');
+  test_invalid('@scope 1px');
+  test_invalid('@scope creep');
+</script>