How to wait for the popup closed event

We do have a button which basically opens a popup. Inside popup, user does some operations and submits data. Once the user clicks in submit button inside the popup, the popup is closed and the flow returns back to the parent window (url route happens)

I wanted to know how do I make sure that the pop up closed or not. Is there any event which I can tag onto or any alternative solution for this ? I need to just write a test case which waits and asserts that the popup closed and proceed to the next test case.