Initial

tests/unit/boundingBox.test.ts

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+import { describe, it, expect } from 'vitest';
+import { computeBoundingBox, boundingBoxRing } from '$domain';
+import type { LatLngTuple } from '$domain';
+
+describe('computeBoundingBox', () => {
+	it('returns null for an empty path', () => {
+		expect(computeBoundingBox([])).toBeNull();
+	});
+
+	it('wraps the extremes and expands by the margin', () => {
+		const path: LatLngTuple[] = [
+			[62.0, 129.0],
+			[62.5, 130.0]
+		];
+		const box = computeBoundingBox(path, 0)!;
+		expect(box.south).toBeCloseTo(62.0, 6);
+		expect(box.north).toBeCloseTo(62.5, 6);
+		expect(box.west).toBeCloseTo(129.0, 6);
+		expect(box.east).toBeCloseTo(130.0, 6);
+
+		const padded = computeBoundingBox(path, 5)!;
+		expect(padded.south).toBeLessThan(62.0);
+		expect(padded.north).toBeGreaterThan(62.5);
+		expect(padded.west).toBeLessThan(129.0);
+		expect(padded.east).toBeGreaterThan(130.0);
+	});
+});
+
+describe('boundingBoxRing', () => {
+	it('is a closed ring of 5 corners (SW repeated)', () => {
+		const ring = boundingBoxRing({ south: 1, west: 2, north: 3, east: 4 });
+		expect(ring).toHaveLength(5);
+		expect(ring[0]).toEqual(ring[4]);
+	});
+});