Added tests for format and storage, run in UK time

web/src/lib/format.test.ts

@@ -0,0 +1,28 @@
+import { expect, test } from 'vitest';
+
+import { formatDate, formatMoney, parseDate } from './format';
+
+test.each([
+  { name: 'null', value: null },
+  { name: 'undefined', value: undefined },
+  { name: 'empty', value: '' },
+  { name: 'Go’s zero time', value: '0001-01-01T00:00:00Z' },
+  { name: 'not a date', value: 'soon' },
+])('parseDate reads $name as no date', ({ value }) => {
+  expect(parseDate(value)).toBeNull();
+  expect(formatDate(value)).toBe('—');
+});
+
+test('dates are shown day, short month and year', () => {
+  // Tests run in UK time (vite.config.ts), as dates are shown in local time.
+  expect(parseDate('2026-03-03T12:00:00Z')?.toISOString()).toBe('2026-03-03T12:00:00.000Z');
+  expect(formatDate('2026-03-03T12:00:00Z')).toBe('3 Mar 2026');
+  // 23:30 UTC is already the next day in British Summer Time.
+  expect(formatDate('2026-07-01T23:30:00Z')).toBe('2 Jul 2026');
+});
+
+test('money is shown in whole pounds, and nothing as a dash', () => {
+  expect(formatMoney(125000.5)).toBe('£125,001');
+  expect(formatMoney(0)).toBe('—');
+  expect(formatMoney(-5)).toBe('—');
+});