test(query-core): use fakeTimers for onlineManager.test.tsx (#8980)

Co-authored-by: Dominik Dorfmeister <office@dorfmeister.cc>

Author: minseong0324

Diff for: packages/query-core/src/__tests__/onlineManager.test.tsx

@@ -1,13 +1,19 @@
-import { beforeEach, describe, expect, test, vi } from 'vitest'
+import { afterEach, beforeEach, describe, expect, test, vi } from 'vitest'
 import { OnlineManager } from '../onlineManager'
-import { setIsServer, sleep } from './utils'
+import { setIsServer } from './utils'
 
 describe('onlineManager', () => {
   let onlineManager: OnlineManager
+
   beforeEach(() => {
+    vi.useFakeTimers()
     onlineManager = new OnlineManager()
   })
 
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
   test('isOnline should return true if navigator is undefined', () => {
     const navigatorSpy = vi.spyOn(globalThis, 'navigator', 'get')
 
@@ -41,7 +47,7 @@ describe('onlineManager', () => {
 
     onlineManager.setEventListener(setup)
 
-    await sleep(30)
+    await vi.advanceTimersByTimeAsync(30)
     expect(count).toEqual(1)
     expect(onlineManager.isOnline()).toBeFalsy()
   })