1 files changed, 48 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Temporal/Duration/prototype/round/dst-rounding-result.js b/js/src/tests/test262/built-ins/Temporal/Duration/prototype/round/dst-rounding-result.js
new file mode 100644
index 0000000000..daff4e93f6
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Temporal/Duration/prototype/round/dst-rounding-result.js
@@ -0,0 +1,48 @@
+// |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.duration.prototype.round
+description: >
+    Rounding the resulting duration takes the time zone's UTC offset shifts
+    into account
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const timeZone = TemporalHelpers.springForwardFallBackTimeZone();
+
+// Based on a test case by Adam Shaw
+
+{
+  // Date part of duration lands on skipped DST hour, causing disambiguation
+  const duration = new Temporal.Duration(0, 1, 0, 15, 12);
+  const relativeTo = new Temporal.ZonedDateTime(
+    950868000_000_000_000n /* = 2000-02-18T10Z */,
+    timeZone); /* = 2000-02-18T02-08 in local time */
+
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", relativeTo }),
+    0, 2, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days 12 hours should be exactly 1.5 months, which rounds up to 2 months");
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", roundingMode: 'halfTrunc', relativeTo }),
+    0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days 12 hours should be exactly 1.5 months, which rounds down to 1 month");
+}
+
+{
+  // Month-only part of duration lands on skipped DST hour, should not cause
+  // disambiguation
+  const duration = new Temporal.Duration(0, 1, 0, 15);
+  const relativeTo = new Temporal.ZonedDateTime(
+    951991200_000_000_000n /* = 2000-03-02T10Z */,
+    timeZone); /* = 2000-03-02T02-08 in local time */
+
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", relativeTo }),
+    0, 2, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days should be exactly 1.5 months, which rounds up to 2 months");
+  TemporalHelpers.assertDuration(duration.round({ smallestUnit: "months", roundingMode: 'halfTrunc', relativeTo }),
+    0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
+    "1 month 15 days should be exactly 1.5 months, which rounds down to 1 month");
+}
+
+reportCompare(0, 0);