1 files changed, 59 insertions, 0 deletions
diff --git a/js/src/tests/test262/harness/temporalHelpers-cross-date-line-time-zone.js b/js/src/tests/test262/harness/temporalHelpers-cross-date-line-time-zone.js
new file mode 100644
index 0000000000..b2c0abd294
--- /dev/null
+++ b/js/src/tests/test262/harness/temporalHelpers-cross-date-line-time-zone.js
@@ -0,0 +1,59 @@
+// |reftest| skip -- Temporal is not supported
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+description: >
+  Verify the time zone arithmetic used in
+  TemporalHelpers.crossDateLineTimeZone() against the Pacific/Apia time zone in
+  the implementation's time zone database
+includes: [compareArray.js, temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// No need to test this on hosts that don't provide an Intl object. It's
+// sufficient that the logic is tested on at least one host.
+if (typeof globalThis.Intl !== "undefined") {
+  const tz = TemporalHelpers.crossDateLineTimeZone();
+  const realTz = new Temporal.TimeZone('Pacific/Apia');
+  const shiftInstant = Temporal.Instant.from('2011-12-30T10:00:00Z');
+
+  assert.sameValue(
+    tz.getOffsetNanosecondsFor(shiftInstant),
+    realTz.getOffsetNanosecondsFor(shiftInstant),
+    'offset at shift instant'
+  );
+  const minus1 = shiftInstant.subtract({ hours: 1 });
+  assert.sameValue(
+    tz.getOffsetNanosecondsFor(minus1),
+    realTz.getOffsetNanosecondsFor(minus1),
+    'offset at 1 hour before shift'
+  );
+  const plus1 = shiftInstant.add({ hours: 1 });
+  assert.sameValue(
+    tz.getOffsetNanosecondsFor(plus1),
+    realTz.getOffsetNanosecondsFor(plus1),
+    'offset at 1 hour after shift'
+  );
+
+  const middleOfSkippedDayWallTime = Temporal.PlainDateTime.from("2011-12-30T12:00");
+  assert.compareArray(
+    tz.getPossibleInstantsFor(middleOfSkippedDayWallTime).map((i) => i.epochNanoseconds),
+    realTz.getPossibleInstantsFor(middleOfSkippedDayWallTime).map((i) => i.epochNanoseconds),
+    'possible instants for middle of skipped day wall time'
+  );
+  const before1 = middleOfSkippedDayWallTime.subtract({ days: 1 });
+  assert.compareArray(
+    tz.getPossibleInstantsFor(before1).map((i) => i.epochNanoseconds),
+    realTz.getPossibleInstantsFor(before1).map((i) => i.epochNanoseconds),
+    'possible instants for 1 day before skipped day'
+  );
+  const after1 = middleOfSkippedDayWallTime.add({ days: 1 });
+  assert.compareArray(
+    tz.getPossibleInstantsFor(after1).map((i) => i.epochNanoseconds),
+    realTz.getPossibleInstantsFor(after1).map((i) => i.epochNanoseconds),
+    'possible instants for 1 day after skipped day'
+  );
+}
+
+reportCompare(0, 0);