Added tests in

tests/time.test.mjs

@@ -0,0 +1,20 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import { formatTime } from '../vr180player/utils/time.js';
+
+test('formatTime formats minute-length durations', () => {
+	assert.equal(formatTime(0), '00:00');
+	assert.equal(formatTime(65), '01:05');
+	assert.equal(formatTime(599), '09:59');
+});
+
+test('formatTime formats hour-length durations', () => {
+	assert.equal(formatTime(3600), '01:00:00');
+	assert.equal(formatTime(3661), '01:01:01');
+});
+
+test('formatTime handles invalid durations defensively', () => {
+	assert.equal(formatTime(Number.NaN), '00:00:00');
+	assert.equal(formatTime(Number.POSITIVE_INFINITY), '00:00:00');
+});