From ba9c3979230ca3f5a54956da9e9b2ba4e2028d4c Mon Sep 17 00:00:00 2001
From: Adam Shaw <arshaw@users.noreply.github.com>
Date: Mon, 13 May 2024 22:12:30 -0400
Subject: [PATCH] tests for
 https://github.com/tc39/proposal-temporal/issues/2820

---
 .../since/wrapping-at-end-of-month.js         | 22 +++++++++++++++++++
 .../until/wrapping-at-end-of-month.js         | 22 +++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/wrapping-at-end-of-month.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/wrapping-at-end-of-month.js
index 2c07323c55..d49cc4edff 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/since/wrapping-at-end-of-month.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/wrapping-at-end-of-month.js
@@ -115,3 +115,25 @@ features: [Temporal]
     "Jan 31st 1970 to May 30th 1971 is 1 year, 3 months, 30 days, not 1 year, 2 months, 60 days"
   );
 }
+
+// Test that 1-day backoff to maintain date/time sign compatibility backs-off from correct end
+// while moving *forwards* in time and does not interfere with month boundaries
+// https://github.com/tc39/proposal-temporal/issues/2820
+{
+  TemporalHelpers.assertDuration(
+    new Temporal.PlainDateTime(2023, 2, 28, 3).since(new Temporal.PlainDateTime(2023, 4, 1, 2), { largestUnit: "years" }),
+    0, -1, 0, -3, -23, 0, 0, 0, 0, 0,
+    "Feb 28th (3am) to Apr 1st (2am) is -1 month, -3 days, and -23 hours"
+  );
+}
+
+// Test that 1-day backoff to maintain date/time sign compatibility backs-off from correct end
+// while moving *backwards* in time and does not interfere with month boundaries
+// https://github.com/tc39/proposal-temporal/issues/2820
+{
+  TemporalHelpers.assertDuration(
+    new Temporal.PlainDateTime(2023, 3, 1, 2).since(new Temporal.PlainDateTime(2023, 1, 1, 3), { largestUnit: "years" }),
+    0, 1, 0, 30, 23, 0, 0, 0, 0, 0,
+    "Mar 1st (2am) to Jan 1st (3am) is 1 month, 30 days, and 23 hours"
+  );
+}
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/wrapping-at-end-of-month.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/wrapping-at-end-of-month.js
index fa534d6020..3300f18a6d 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/until/wrapping-at-end-of-month.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/wrapping-at-end-of-month.js
@@ -115,3 +115,25 @@ features: [Temporal]
     "Jan 31st 1970 to May 30th 1971 is 1 year, 3 months, 30 days, not 1 year, 2 months, 60 days"
   );
 }
+
+// Test that 1-day backoff to maintain date/time sign compatibility backs-off from correct end
+// while moving *backwards* in time and does not interfere with month boundaries
+// https://github.com/tc39/proposal-temporal/issues/2820
+{
+  TemporalHelpers.assertDuration(
+    new Temporal.PlainDateTime(2023, 2, 28, 3).until(new Temporal.PlainDateTime(2023, 4, 1, 2), { largestUnit: "years" }),
+    0, 1, 0, 3, 23, 0, 0, 0, 0, 0,
+    "Feb 28th (3am) to Apr 1st (2am) is 1 month, 3 days, and 23 hours"
+  );
+}
+
+// Test that 1-day backoff to maintain date/time sign compatibility backs-off from correct end
+// while moving *forwards* in time and does not interfere with month boundaries
+// https://github.com/tc39/proposal-temporal/issues/2820
+{
+  TemporalHelpers.assertDuration(
+    new Temporal.PlainDateTime(2023, 3, 1, 2).until(new Temporal.PlainDateTime(2023, 1, 1, 3), { largestUnit: "years" }),
+    0, -1, 0, -30, -23, 0, 0, 0, 0, 0,
+    "Mar 1st (2am) to Jan 1st (3am) is -1 month, -30 days, and -23 hours"
+  );
+}