1 files changed, 84 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Temporal/ZonedDateTime/prototype/since/find-intermediate-instant.js b/js/src/tests/test262/built-ins/Temporal/ZonedDateTime/prototype/since/find-intermediate-instant.js
new file mode 100644
index 0000000000..7ef187ce3b
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Temporal/ZonedDateTime/prototype/since/find-intermediate-instant.js
@@ -0,0 +1,84 @@
+// |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.zoneddatetime.prototype.until
+description: >
+  Up to 3 intermediate instants may be tried when calculating ZonedDateTime
+  difference
+includes: [compareArray.js, temporalHelpers.js]
+features: [BigInt, Temporal]
+---*/
+
+const calls = [];
+
+const springFallZone = TemporalHelpers.springForwardFallBackTimeZone();
+TemporalHelpers.observeMethod(calls, springFallZone, "getPossibleInstantsFor");
+
+const dateLineZone = TemporalHelpers.crossDateLineTimeZone();
+TemporalHelpers.observeMethod(calls, dateLineZone, "getPossibleInstantsFor");
+
+const zdt2 = new Temporal.ZonedDateTime(946722600_000_000_000n /* = 2000-01-01T02:30 local */, springFallZone);
+
+// Future -> past, without wall-clock overshoot
+// Expects valid intermediate Instant WITHOUT day correction (computed once)
+{
+  const zdt1 = new Temporal.ZonedDateTime(949442400_000_000_000n /* = 2000-02-01T14:00 local */, springFallZone);
+  const result = zdt1.since(zdt2, { largestUnit: "years" });
+  TemporalHelpers.assertDuration(result, 0, 1, 0, 0, 11, 30, 0, 0, 0, 0, "no wall-clock overshoot, no DST");
+  assert.compareArray(calls, [
+    "call getPossibleInstantsFor",  // first intermediate in DifferenceZonedDateTime
+  ], "one intermediate should be tried");
+}
+
+calls.splice(0);  // clear
+
+// Future -> past, WITH wall-clock overshoot
+// Expects valid intermediate Instant with guaranteed 1-DAY correction (computed once)
+{
+  const zdt1 = new Temporal.ZonedDateTime(949395600_000_000_000n /* = 2000-02-01T01:00 local */, springFallZone);
+  const result = zdt1.since(zdt2, { largestUnit: "years" });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 30, 22, 30, 0, 0, 0, 0, "wall-clock overshoot, no DST");
+  assert.compareArray(calls, [
+    "call getPossibleInstantsFor",  // first intermediate in DifferenceZonedDateTime
+  ], "one intermediate should be tried");
+}
+
+calls.splice(0);  // clear
+
+// Future -> past, WITH wall-clock overshoot
+// Expects valid intermediate Instant with guaranteed 1-DAY correction (computed once)
+// Intermediate Instant falls within spring DST gap and gets pushed forward,
+// but since moving from future -> past, not possible to exacerbate overflow,
+// so no other day corrections.
+{
+  const end = new Temporal.ZonedDateTime(957258000_000_000_000n /* = 2000-05-02T02:00 local */, springFallZone);
+  const start = new Temporal.ZonedDateTime(954671400_000_000_000n /* = 2000-04-02T03:30-07:00 local */, springFallZone);
+  const result = end.since(start, { largestUnit: "years" });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 29, 22, 30, 0, 0, 0, 0, "wall-clock overshoot, inconsiquential DST");
+  assert.compareArray(calls, [
+    "call getPossibleInstantsFor",  // first intermediate in DifferenceZonedDateTime
+  ], "one intermediate should be tried");
+}
+
+calls.splice(0);  // clear
+
+// Past -> future, WITH wall-clock overshoot
+// Tries intermediate Instant with 1-DAY correction (first compute)
+// Then, ANOTHER day correction because updated intermediate Instant falls within dateline DST gap,
+// pushing it forward, causing wall-clock overshoot again
+// (Not possible when going backwards)
+// (This test is just the same as the corresponding one in until(), but negative)
+{
+  const start = new Temporal.ZonedDateTime(1325102400_000_000_000n /* = 2011-12-28T10:00 local */, dateLineZone);
+  const end = new Temporal.ZonedDateTime(1325257200_000_000_000n /* = 2011-12-31T05:00 local */, dateLineZone);
+  const result = start.since(end, { largestUnit: "days" });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, -1, -19, 0, 0, 0, 0, 0, "wall-clock overshoot, consiquential DST");
+  assert.compareArray(calls, [
+    "call getPossibleInstantsFor",  // first intermediate in DifferenceZonedDateTime
+    "call getPossibleInstantsFor",  // second intermediate in DifferenceZonedDateTime
+    "call getPossibleInstantsFor",  // DisambiguatePossibleInstants on second intermediate
+  ], "two intermediates should be tried, with disambiguation");
+}
+
+reportCompare(0, 0);