1 files changed, 32 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Temporal/Instant/compare/argument-string-calendar-annotation-invalid-key.js b/js/src/tests/test262/built-ins/Temporal/Instant/compare/argument-string-calendar-annotation-invalid-key.js
new file mode 100644
index 0000000000..a0863e12f6
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Temporal/Instant/compare/argument-string-calendar-annotation-invalid-key.js
@@ -0,0 +1,32 @@
+// |reftest| skip-if(!this.hasOwnProperty('Temporal')) -- Temporal is not enabled unconditionally
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.compare
+description: Annotation keys are lowercase-only 
+features: [Temporal]
+---*/
+
+const epoch = new Temporal.Instant(0n);
+
+const invalidStrings = [
+  ["1970-01-01T00:00Z[U-CA=iso8601]", "invalid capitalized key"],
+  ["1970-01-01T00:00Z[u-CA=iso8601]", "invalid partially-capitalized key"],
+  ["1970-01-01T00:00Z[FOO=bar]", "invalid capitalized unrecognized key"],
+];
+
+invalidStrings.forEach(([arg, descr]) => {
+  assert.throws(
+    RangeError,
+    () => Temporal.Instant.compare(arg, epoch),
+    `annotation keys must be lowercase: ${arg} - ${descr} (first argument)`
+  );
+  assert.throws(
+    RangeError,
+    () => Temporal.Instant.compare(epoch, arg),
+    `annotation keys must be lowercase: ${arg} - ${descr} (second argument)`
+  );
+});
+
+reportCompare(0, 0);