test: add test for dateutil

test/dateutil.test.ts

@@ -0,0 +1,56 @@
+import tap from 'tap';
+import { formatDateTime } from '../src/lib/dateutil';
+
+tap.test('formatDateTime', async (t) => {
+  t.test('formats date with default format', async (t) => {
+    const date = new Date('2023-04-15T14:30:45Z');
+    t.equal(
+      formatDateTime(date, 'MMMM Do, YYYY h:mm:ss a z'),
+      'April 15th, 2023 2:30:45 pm UTC',
+    );
+    t.end();
+  });
+
+  t.test('handles different months', async (t) => {
+    const date = new Date('2023-01-01T00:00:00Z');
+    t.equal(formatDateTime(date, 'MMMM Do, YYYY'), 'January 1st, 2023');
+    t.end();
+  });
+
+  t.test('handles ordinal suffixes correctly', async (t) => {
+    t.equal(formatDateTime(new Date('2023-05-01T00:00:00Z'), 'Do'), '1st');
+    t.equal(formatDateTime(new Date('2023-05-02T00:00:00Z'), 'Do'), '2nd');
+    t.equal(formatDateTime(new Date('2023-05-03T00:00:00Z'), 'Do'), '3rd');
+    t.equal(formatDateTime(new Date('2023-05-04T00:00:00Z'), 'Do'), '4th');
+    t.equal(formatDateTime(new Date('2023-05-11T00:00:00Z'), 'Do'), '11th');
+    t.equal(formatDateTime(new Date('2023-05-21T00:00:00Z'), 'Do'), '21st');
+    t.end();
+  });
+
+  t.test('formats time correctly', async (t) => {
+    const date = new Date('2023-04-15T23:59:59Z');
+    t.equal(formatDateTime(date, 'h:mm:ss a'), '11:59:59 pm');
+    t.end();
+  });
+
+  t.test('handles midnight correctly', async (t) => {
+    const date = new Date('2023-04-15T00:00:00Z');
+    t.equal(formatDateTime(date, 'h:mm:ss a'), '12:00:00 am');
+    t.end();
+  });
+
+  t.test('includes timezone information', async (t) => {
+    const date = new Date('2023-04-15T14:30:45Z');
+    t.equal(formatDateTime(date, 'z Z'), 'UTC +00:00');
+    t.end();
+  });
+
+  t.test('uses current date when no date is provided', async (t) => {
+    const now = new Date();
+    const formatted = formatDateTime(null, 'YYYY');
+    t.equal(formatted, now.getUTCFullYear().toString());
+    t.end();
+  });
+
+  t.end();
+});