as I play nowadays a lot with layout of one of installation dialog I need to effectively test it. For runtime you can always use just resize of window and see various results. For installation it is a bit different as installation runs fullscreen. I use for testing virt-manager and runs VM on our server. So for various resolution you can use F3 on grub screen after boot to play with different resolutions ( just pick "Installer size" and not others like me ). For testing ncurses you can enable there text mode and if minimal console needs to be tested then combination of Text Mode and Text Console Size No KMS do the trick for me.
HuHa tip: you can use same approach as for runtime testing, just use ssh installation either with X forwarding or without and resize your ssh window.