Manipulate pop up, opened by the cypress runner

[iwcpaulis]

I'd like to manipulate a pop up - not a pop over! -, which get open by the runner.
But nowhere I found any source in docs.cypress.io that tells me specificly, that to manipulate pop ups is not possible or is possible.

Would be nice, if anybody can show me the direction, where I can find information about pop ups. Thank you!