Refine live control and show overview

src/lib/calendar.spec.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it } from 'vitest';
+import {
+	berlinDateKey,
+	buildCalendarDays,
+	formatMonthLabel,
+	normalizeMonthKey,
+	shiftMonth
+} from './calendar.js';
+
+describe('show calendar', () => {
+	it('groups UTC instants by their Berlin civil date', () => {
+		expect(berlinDateKey('2026-09-30T22:30:00.000Z')).toBe('2026-10-01');
+		expect(berlinDateKey('2026-12-31T23:30:00.000Z')).toBe('2027-01-01');
+	});
+
+	it('builds a Monday-first six-week month without dropping boundary days', () => {
+		const days = buildCalendarDays('2026-10', '2026-10-24');
+		expect(days).toHaveLength(42);
+		expect(days[0]).toMatchObject({ date: '2026-09-28', inSelectedMonth: false });
+		expect(days.find((day) => day.date === '2026-10-24')?.isToday).toBe(true);
+		expect(days.at(-1)?.date).toBe('2026-11-08');
+	});
+
+	it('moves across year boundaries and validates month keys', () => {
+		expect(shiftMonth('2026-12', 1)).toBe('2027-01');
+		expect(shiftMonth('2026-01', -1)).toBe('2025-12');
+		expect(normalizeMonthKey('2026-13', '2026-10')).toBe('2026-10');
+		expect(normalizeMonthKey('2026-02', '2026-10')).toBe('2026-02');
+		expect(formatMonthLabel('2026-10')).toBe('Oktober 2026');
+	});
+});