[scheduler] Add tests for the sortOccurrences utility (#20605)

Author: flaviendelangle

packages/x-scheduler-headless/src/sort-event-occurrences/sortEventOccurrences.test.ts

@@ -0,0 +1,197 @@
+import { adapter, EventBuilder } from 'test/utils/scheduler';
+import { sortEventOccurrences } from './sortEventOccurrences';
+
+describe('sortEventOccurrences', () => {
+  describe('basic sorting', () => {
+    it('should return empty array when given empty array', () => {
+      expect(sortEventOccurrences([], adapter)).toEqual([]);
+    });
+
+    it('should return single occurrence unchanged', () => {
+      const occurrence = EventBuilder.new().singleDay('2024-01-15T10:00:00').toOccurrence();
+      expect(sortEventOccurrences([occurrence], adapter)).toEqual([occurrence]);
+    });
+
+    it('should sort occurrences by start date (earliest first)', () => {
+      const first = EventBuilder.new().id('first').singleDay('2024-01-15T08:00:00').toOccurrence();
+      const second = EventBuilder.new()
+        .id('second')
+        .singleDay('2024-01-15T10:00:00')
+        .toOccurrence();
+      const third = EventBuilder.new().id('third').singleDay('2024-01-15T14:00:00').toOccurrence();
+
+      expect(sortEventOccurrences([third, first, second], adapter)).to.deep.equal([
+        first,
+        second,
+        third,
+      ]);
+    });
+  });
+
+  describe('same start date tiebreaker', () => {
+    it('should sort by end date (later end first) when start dates are equal', () => {
+      const short = EventBuilder.new()
+        .id('short')
+        .singleDay('2024-01-15T10:00:00', 30)
+        .toOccurrence();
+      const long = EventBuilder.new()
+        .id('long')
+        .singleDay('2024-01-15T10:00:00', 120)
+        .toOccurrence();
+
+      expect(sortEventOccurrences([short, long], adapter)).to.deep.equal([long, short]);
+    });
+
+    it('should handle multiple events with same start but different ends', () => {
+      const short = EventBuilder.new()
+        .id('short')
+        .singleDay('2024-01-15T10:00:00', 30)
+        .toOccurrence();
+      const medium = EventBuilder.new()
+        .id('medium')
+        .singleDay('2024-01-15T10:00:00')
+        .toOccurrence();
+      const long = EventBuilder.new()
+        .id('long')
+        .singleDay('2024-01-15T10:00:00', 120)
+        .toOccurrence();
+
+      expect(sortEventOccurrences([short, medium, long], adapter)).to.deep.equal([
+        long,
+        medium,
+        short,
+      ]);
+    });
+  });
+
+  describe('all-day events', () => {
+    it('should sort all-day events by start of day', () => {
+      const day1 = EventBuilder.new()
+        .id('day1')
+        .span('2024-01-15T00:00:00', '2024-01-15T23:59:59')
+        .allDay(true)
+        .toOccurrence();
+      const day2 = EventBuilder.new()
+        .id('day2')
+        .span('2024-01-16T00:00:00', '2024-01-16T23:59:59')
+        .allDay(true)
+        .toOccurrence();
+
+      expect(sortEventOccurrences([day2, day1], adapter)).to.deep.equal([day1, day2]);
+    });
+
+    it('should sort all-day events with same start by end date (longer first)', () => {
+      const singleDay = EventBuilder.new()
+        .id('single')
+        .span('2024-01-15T00:00:00', '2024-01-15T23:59:59')
+        .allDay(true)
+        .toOccurrence();
+      const multiDay = EventBuilder.new()
+        .id('multi')
+        .span('2024-01-15T00:00:00', '2024-01-17T23:59:59')
+        .allDay(true)
+        .toOccurrence();
+
+      expect(sortEventOccurrences([singleDay, multiDay], adapter)).to.deep.equal([
+        multiDay,
+        singleDay,
+      ]);
+    });
+  });
+
+  describe('mixed timed and all-day events', () => {
+    it('should correctly sort mixed all-day and timed events on the same day', () => {
+      const allDay = EventBuilder.new()
+        .id('allDay')
+        .span('2024-01-15T00:00:00', '2024-01-15T23:59:59')
+        .allDay(true)
+        .toOccurrence();
+      const timed = EventBuilder.new().id('timed').singleDay('2024-01-15T10:00:00').toOccurrence();
+
+      // All-day event starts at midnight (start of day), so it should come first
+      expect(sortEventOccurrences([timed, allDay], adapter)).to.deep.equal([allDay, timed]);
+    });
+
+    it('should sort all-day event after timed event that starts earlier in the day', () => {
+      const allDay = EventBuilder.new()
+        .id('allDay')
+        .span('2024-01-16T00:00:00', '2024-01-16T23:59:59')
+        .allDay(true)
+        .toOccurrence();
+      const timedEarlier = EventBuilder.new()
+        .id('timed')
+        .singleDay('2024-01-15T10:00:00')
+        .toOccurrence();
+
+      expect(sortEventOccurrences([allDay, timedEarlier], adapter)).to.deep.equal([
+        timedEarlier,
+        allDay,
+      ]);
+    });
+  });
+
+  describe('edge cases', () => {
+    it('should maintain stable sort for identical occurrences', () => {
+      // Two events with exactly the same start and end
+      const event1 = EventBuilder.new()
+        .id('event1')
+        .singleDay('2024-01-15T10:00:00')
+        .toOccurrence();
+      const event2 = EventBuilder.new()
+        .id('event2')
+        .singleDay('2024-01-15T10:00:00')
+        .toOccurrence();
+
+      // Should maintain original order when equal
+      expect(sortEventOccurrences([event1, event2], adapter)).to.deep.equal([event1, event2]);
+    });
+
+    it('should handle events spanning multiple days', () => {
+      const multiDay = EventBuilder.new()
+        .id('multiDay')
+        .span('2024-01-15T10:00:00', '2024-01-17T14:00:00')
+        .toOccurrence();
+      const singleDay = EventBuilder.new()
+        .id('singleDay')
+        .singleDay('2024-01-15T12:00:00')
+        .toOccurrence();
+
+      // multiDay starts earlier (10:00), so it should come first
+      expect(sortEventOccurrences([singleDay, multiDay], adapter)).to.deep.equal([
+        multiDay,
+        singleDay,
+      ]);
+    });
+
+    it('should handle events on different days', () => {
+      const monday = EventBuilder.new()
+        .id('monday')
+        .singleDay('2024-01-15T10:00:00')
+        .toOccurrence();
+      const wednesday = EventBuilder.new()
+        .id('wednesday')
+        .singleDay('2024-01-17T10:00:00')
+        .toOccurrence();
+      const tuesday = EventBuilder.new()
+        .id('tuesday')
+        .singleDay('2024-01-16T10:00:00')
+        .toOccurrence();
+
+      expect(sortEventOccurrences([wednesday, monday, tuesday], adapter)).to.deep.equal([
+        monday,
+        tuesday,
+        wednesday,
+      ]);
+    });
+
+    it('should not mutate the original array', () => {
+      const early = EventBuilder.new().id('early').singleDay('2024-01-15T08:00:00').toOccurrence();
+      const late = EventBuilder.new().id('late').singleDay('2024-01-15T14:00:00').toOccurrence();
+
+      const original = [late, early];
+
+      expect(sortEventOccurrences(original, adapter)).to.deep.equal([early, late]);
+      expect(original).to.deep.equal([late, early]);
+    });
+  });
+});