detectAsyncLeaks

Type: boolean
CLI: --detectAsyncLeaks, --detect-async-leaks
Default: false

WARNING

Enabling this option will make your tests run much slower. Use only when debugging or developing tests.

Detect asynchronous resources leaking from the test file. Uses node:async_hooks to track creation of async resources. If a resource is not cleaned up, it will be logged after tests have finished.

For example if your code has setTimeout calls that execute the callback after tests have finished, you will see following error:

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Async Leaks 1 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

Timeout leaking in test/checkout-screen.test.tsx
 26|
 27|   useEffect(() => {
 28|     setTimeout(() => setWindowWidth(window.innerWidth), 150)
   |     ^
 29|   })
 30|

To fix this, you'll need to make sure your code cleans the timeout properly:

useEffect(() => {
  setTimeout(() => setWindowWidth(window.innerWidth), 150) 
  const timeout = setTimeout(() => setWindowWidth(window.innerWidth), 150) 

  return function cleanup() { 
    clearTimeout(timeout) 
  } 
})

detectAsyncLeaks ​

detectAsyncLeaks