support "11 months" and fix tests

Author: wxiaoguang

src/duration.ts

@@ -179,12 +179,9 @@ export function roundToSingleUnit(duration: Duration, {relativeTo = Date.now()}:
         days = daysDiff
       }
       months = years = 0
-    } else if (monthsDiff < 11) {
+    } else if (monthsDiff <= 11) {
       months = monthsDiff
       years = 0
-    } else if (monthsDiff === 11) {
-      months = 0
-      years += 1 // the old behavior: "11 months" is rounded to "1 year"
     } else {
       months = 0
       years = yearDiff * sign

test/duration.ts

@@ -291,8 +291,8 @@ suite('duration', function () {
         },
       ],
       ['P9M20DT25H', 'P10M', {relativeTo: new Date('2023-01-12T00:00:00Z')}],
-      ['P11M', 'P1Y', {relativeTo: new Date('2022-11-01T00:00:00Z')}],
-      ['-P11M', '-P1Y', {relativeTo: new Date('2022-11-01T00:00:00Z')}],
+      ['P11M', 'P11M', {relativeTo: new Date('2022-11-01T00:00:00Z')}],
+      ['-P11M', '-P11M', {relativeTo: new Date('2022-11-01T00:00:00Z')}],
       ['-P11M15D', '-P1Y', {relativeTo: new Date('2024-01-06T00:00:00')}],
       ['P1Y4D', 'P1Y', {relativeTo: new Date('2022-11-01T00:00:00Z')}],
       ['P1Y5M13D', 'P1Y', {relativeTo: new Date('2023-01-01T00:00:00Z')}],
@@ -429,7 +429,7 @@ suite('duration', function () {
           relativeTo: new Date('2022-12-01T00:00:00Z'),
         },
       ],
-      ['P11M', [1, 'year']],
+      ['P11M', [11, 'month']],
       ['P1Y4D', [1, 'year']],
       [
         'P1Y5M13D',

test/relative-time.js

@@ -2503,7 +2503,7 @@ suite('relative-time', function () {
         datetime: '2024-01-16T00:00:00.000Z',
         tense: 'past',
         format: 'auto',
-        expected: 'last year', // a quick fix for the old bug: "23 days ago" because "11 months" was discarded, ideally it should support "11 months"
+        expected: '11 months ago',
       },
     ])