Tests for Duration rounding bug when rounding crosses a unit boundary

See tc39/proposal-temporal#2563

The old behaviour was encoded in one test in staging, but the behaviour of
largestUnit in duration rounding has changed since that test was written.
Therefore I'm assuming that toString() should've been updated when that
happened.

test/built-ins/Temporal/Duration/prototype/round/round-cross-unit-boundary.js

@@ -0,0 +1,47 @@
+// Copyright (C) 2023 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 can cross unit boundaries up to the implicit largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const relativeTo = new Temporal.PlainDate(2022, 1, 1);
+const roundingMode = "expand";
+
+// Positive, date units
+{
+  const duration = new Temporal.Duration(1, 11, 0, 24);
+  const result = duration.round({ smallestUnit: "months", roundingMode, relativeTo });
+  TemporalHelpers.assertDuration(result, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 12 months balances to 2 years");
+}
+
+// Negative, date units
+{
+  const duration = new Temporal.Duration(-1, -11, 0, -24);
+  const result = duration.round({ smallestUnit: "months", roundingMode, relativeTo });
+  TemporalHelpers.assertDuration(result, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -12 months balances to -2 years");
+}
+
+// Positive, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 1, 59, 59, 900);
+  const result = duration.round({ smallestUnit: "seconds", roundingMode });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59:60 balances to 2 hours");
+}
+
+// Negative, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, -1, -59, -59, -900);
+  const result = duration.round({ smallestUnit: "seconds", roundingMode });
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59:60 balances to -2 hours");
+}
+
+// No balancing if smallest unit is largest unit
+{
+  const duration = new Temporal.Duration(0, 11, 0, 24);
+  const result = duration.round({ smallestUnit: "months", roundingMode, relativeTo });
+  TemporalHelpers.assertDuration(result, 0, 12, 0, 0, 0, 0, 0, 0, 0, 0, "12 months stays as is");
+}

test/built-ins/Temporal/Duration/prototype/toString/round-cross-unit-boundary.js

@@ -0,0 +1,40 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.tostring
+description: Rounding can cross unit boundaries up to days
+features: [Temporal]
+---*/
+
+const roundingMode = "expand";
+
+// Positive, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 1, 59, 59, 900);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 0, roundingMode }), "PT2H0S", "1:59:60 balances to 2 hours");
+}
+
+// Negative, time units
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, -1, -59, -59, -900);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 0, roundingMode }), "-PT2H0S", "-1:59:60 balances to -2 hours");
+}
+
+// Positive, date and time units
+{
+  const duration = new Temporal.Duration(1, 11, 0, 30, 23, 59, 59, 999, 999, 999);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 8, roundingMode }), "P1Y11M31DT0.00000000S", "units balance only up to days (positive)");
+}
+
+// Negative, date and time units
+{
+  const duration = new Temporal.Duration(-1, -11, 0, -30, -23, -59, -59, -999, -999, -999);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 8, roundingMode }), "-P1Y11M31DT0.00000000S", "units balance only up to days (negative)");
+}
+
+// No balancing if smallest unit is largest unit
+{
+  const duration = new Temporal.Duration(0, 0, 0, 0, 0, 0, 59, 900);
+  assert.sameValue(duration.toString({ fractionalSecondDigits: 0, roundingMode }), "PT60S", "60 seconds stays as is");
+}

test/built-ins/Temporal/Instant/prototype/since/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.Instant(0n);
+const later = new Temporal.Instant(7199_000_000_000n);
+const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59 balances to -2 hours");

test/built-ins/Temporal/Instant/prototype/until/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.Instant(0n);
+const later = new Temporal.Instant(7199_000_000_000n);
+const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59 balances to 2 hours");

test/built-ins/Temporal/PlainDate/prototype/since/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainDate(2022, 1, 1);
+const later = new Temporal.PlainDate(2023, 12, 25);
+const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -11 months balances to -2 years");

test/built-ins/Temporal/PlainDate/prototype/until/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainDate(2022, 1, 1);
+const later = new Temporal.PlainDate(2023, 12, 25);
+const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 11 months balances to 2 years");

test/built-ins/Temporal/PlainDateTime/prototype/since/round-cross-unit-boundary.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.PlainDateTime(2022, 1, 1);
+  const later = new Temporal.PlainDateTime(2023, 12, 25);
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -11 months balances to -2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.PlainDateTime(2000, 5, 2);
+  const later = new Temporal.PlainDateTime(2000, 5, 2, 1, 59, 59);
+  const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59 balances to -2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.PlainDateTime(1970, 1, 1);
+  const later = new Temporal.PlainDateTime(1971, 12, 31, 23, 59, 59, 999, 999, 999);
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding down 1 ns balances to -2 years");
+}

test/built-ins/Temporal/PlainDateTime/prototype/until/round-cross-unit-boundary.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.PlainDateTime(2022, 1, 1);
+  const later = new Temporal.PlainDateTime(2023, 12, 25);
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 11 months balances to 2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.PlainDateTime(2000, 5, 2);
+  const later = new Temporal.PlainDateTime(2000, 5, 2, 1, 59, 59);
+  const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59 balances to 2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.PlainDateTime(1970, 1, 1);
+  const later = new Temporal.PlainDateTime(1971, 12, 31, 23, 59, 59, 999, 999, 999);
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding up 1 ns balances to 2 years");
+}

test/built-ins/Temporal/PlainTime/prototype/since/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainTime();
+const later = new Temporal.PlainTime(1, 59, 59);
+const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:60 balances to -2 hours");

test/built-ins/Temporal/PlainTime/prototype/until/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainTime();
+const later = new Temporal.PlainTime(1, 59, 59);
+const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:60 balances to 2 hours");

test/built-ins/Temporal/PlainYearMonth/prototype/since/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainYearMonth(2022, 1);
+const later = new Temporal.PlainYearMonth(2023, 12);
+const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingIncrement: 3, roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -12 months balances to -2 years");

test/built-ins/Temporal/PlainYearMonth/prototype/until/round-cross-unit-boundary.js

@@ -0,0 +1,14 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const earlier = new Temporal.PlainYearMonth(2022, 1);
+const later = new Temporal.PlainYearMonth(2023, 12);
+const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingIncrement: 3, roundingMode: "expand" });
+TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 12 months balances to 2 years");

test/built-ins/Temporal/ZonedDateTime/prototype/since/round-cross-unit-boundary.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2023 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.ZonedDateTime(1640995200_000_000_000n /* = 2022-01-01T00 */, "UTC");
+  const later = new Temporal.ZonedDateTime(1703462400_000_000_000n /* = 2023-12-25T00 */, "UTC");
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "-1 year -11 months balances to -2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(7199_000_000_000n, "UTC");
+  const duration = earlier.since(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, "-1:59 balances to -2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(63071999_999_999_999n /* = 1971-12-31T23:59:59.999999999 */, "UTC");
+  const duration = earlier.since(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, -2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding down 1 ns balances to -2 years");
+}

test/built-ins/Temporal/ZonedDateTime/prototype/until/round-cross-unit-boundary.js

@@ -0,0 +1,33 @@
+// Copyright (C) 2023 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: Rounding can cross unit boundaries up to largestUnit
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Date units
+{
+  const earlier = new Temporal.ZonedDateTime(1640995200_000_000_000n /* = 2022-01-01T00 */, "UTC");
+  const later = new Temporal.ZonedDateTime(1703462400_000_000_000n /* = 2023-12-25T00 */, "UTC");
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "months", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1 year 11 months balances to 2 years");
+}
+
+// Time units
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(7199_000_000_000n, "UTC");
+  const duration = earlier.until(later, { largestUnit: "hours", smallestUnit: "minutes", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, "1:59 balances to 2 hours");
+}
+
+// Both
+{
+  const earlier = new Temporal.ZonedDateTime(0n, "UTC");
+  const later = new Temporal.ZonedDateTime(63071999_999_999_999n /* = 1971-12-31T23:59:59.999999999 */, "UTC");
+  const duration = earlier.until(later, { largestUnit: "years", smallestUnit: "microseconds", roundingMode: "expand" });
+  TemporalHelpers.assertDuration(duration, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "rounding up 1 ns balances to 2 years");
+}

test/staging/Temporal/Duration/old/toString.js

@@ -23,10 +23,3 @@ var d = Temporal.Duration.from({
   microseconds: Number.MAX_SAFE_INTEGER
 });
 assert.sameValue(`${ d }`, "PT9016206453995.731991S");
-
-// rounding can affect units up to seconds
-var d4 = Temporal.Duration.from("P1Y1M1W1DT23H59M59.999999999S");
-assert.sameValue(d4.toString({
-  fractionalSecondDigits: 8,
-  roundingMode: "halfExpand"
-}), "P1Y1M1W1DT23H59M60.00000000S");