test(stammbaum): tidyTree nests deep and shallow siblings without overlap (#724)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/person/genealogy/layout/tidyTree.test.ts

@@ -18,6 +18,36 @@ function center(x: Map<string, number>, n: TidyNode): number {
 	return x.get(n.id)! + n.width / 2;
 }
 
+// Walk a forest, recording each node's tree depth and width.
+function depths(roots: TidyNode[]): Map<string, { depth: number; width: number }> {
+	const out = new Map<string, { depth: number; width: number }>();
+	const walk = (n: TidyNode, d: number) => {
+		out.set(n.id, { depth: d, width: n.width });
+		for (const c of n.children) walk(c, d + 1);
+	};
+	for (const r of roots) walk(r, 0);
+	return out;
+}
+
+// Assert no two boxes at the same depth overlap (clearance >= gap).
+function expectNoOverlap(x: Map<string, number>, roots: TidyNode[], gap: number) {
+	const meta = depths(roots);
+	const ids = [...x.keys()];
+	for (let i = 0; i < ids.length; i++) {
+		for (let j = i + 1; j < ids.length; j++) {
+			const a = meta.get(ids[i])!;
+			const b = meta.get(ids[j])!;
+			if (a.depth !== b.depth) continue;
+			const xa = x.get(ids[i])!;
+			const xb = x.get(ids[j])!;
+			const lo = Math.min(xa, xb);
+			const hi = Math.max(xa, xb);
+			const loW = xa <= xb ? a.width : b.width;
+			expect(hi - lo).toBeGreaterThanOrEqual(loW + gap);
+		}
+	}
+}
+
 describe('tidyTree — leaf base case', () => {
 	it('a single leaf lays out at x = 0', () => {
 		const a = leaf('a');
@@ -45,3 +75,25 @@ describe('tidyTree — ancestor centring', () => {
 		expect(Math.abs(x.get('c2')! - x.get('c1')!)).toBeGreaterThanOrEqual(W + GAP);
 	});
 });
+
+describe('tidyTree — contour nesting', () => {
+	it('a deep subtree and a shallow sibling nest without overlap', () => {
+		// root
+		//  ├─ a (leaf)
+		//  └─ b ─ b1, b2  (deeper)
+		// The contour push must keep b's whole subtree clear of leaf a, and a
+		// clear of b's grandchildren, at every depth.
+		const a = leaf('a');
+		const b = node('b', [leaf('b1'), leaf('b2')]);
+		const root = node('root', [a, b]);
+		const x = layoutForest([root], GAP);
+
+		expectNoOverlap(x, [root], GAP);
+		// Each parent still centred over its own children.
+		expect(center(x, b)).toBe(
+			(center(x, { id: 'b1', width: W, children: [] }) +
+				center(x, { id: 'b2', width: W, children: [] })) /
+				2
+		);
+	});
+});