when-am-i / files / src / utils / lanes.test.ts

lanes.test.ts

1	import { describe, it, expect } from 'vitest';
2	import { assignLanes } from './lanes';
3
4	interface Span { start: number; end: number; }
5	const lane = (spans: Span[]) =>
6	assignLanes(spans, (s) => s.start, (s) => s.end);
7
8	describe('assignLanes', () => {
9	it('puts non-overlapping, adjacent intervals in the same lane', () => {
10	const { lanes, count } = lane([
11	{ start: 1630, end: 1752 },
12	{ start: 1752, end: Infinity }, // half-open: shares the lane
13	]);
14	expect(count).toBe(1);
15	expect(lanes.map((l) => l.lane)).toEqual([0, 0]);
16	});
17
18	it('puts overlapping intervals in separate lanes', () => {
19	const { lanes, count } = lane([
20	{ start: -Infinity, end: Infinity }, // spans everything
21	{ start: 1630, end: 1752 },
22	{ start: 1752, end: Infinity },
23	]);
24	expect(count).toBe(2);
25	// The all-spanning interval gets its own lane; the two adjacent ones share the other.
26	const byOrder = lanes.sort((a, b) => a.item.start - b.item.start).map((l) => l.lane);
27	expect(byOrder[0]).not.toBe(byOrder[1]); // spanning vs 1630
28	expect(byOrder[1]).toBe(byOrder[2]); // 1630 and 1752 share
29	});
30
31	it('opens a third lane when three intervals overlap at once', () => {
32	const { count } = lane([
33	{ start: 0, end: 10 },
34	{ start: 5, end: 15 },
35	{ start: 8, end: 20 },
36	]);
37	expect(count).toBe(3);
38	});
39	});