ENH - clock app

frontend/src/utils/clock.test.ts

@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'vitest'
 import {
   elapsedMilliseconds,
+  formatStopwatch,
   formatTimer,
   remainingMilliseconds,
   timerPickerMilliseconds,
@@ -18,4 +19,8 @@ describe('timestamp clocks', () => {
     expect(timerPickerValue(3_661_000)).toBe('01:01:01')
     expect(timerPickerMilliseconds('01:01:01')).toBe(3_661_000)
   })
+
+  it('formats stopwatch durations with actual milliseconds', () => {
+    expect(formatStopwatch(61_234)).toBe('01:01.234')
+  })
 })