TestFX can I test more fxml files in 1 test.

Hello I new to testing and want to ask something about it. I want to test my project which have like 25 fxml files. Can I test whole project. Not only 1 by 1 fxml file? For example I load first fxml file and there is a button "login" for example and it's going to open another fxml file something like mainMenu.

So I have 1 window and it's open another window. Can I somehow test it?

thank you