Any time there's a combinatorical number, you haven't factored the problem. The custom screen has 4 things: 3 buttons and an image. You have two kinds of thing

Any time there's a combinatorical number, you haven't factored the problem. The custom screen has 4 things: 3 buttons and an image. You have two kinds of things: button and image. The button can have language localization: English, Spanish, French Each of the above things should be tested for what makes it different from other similar things. Not everything should need to be tested in all ways, all the way down. Each thing should as much as possible validate its possible inputs. E.g. if you use any static type information, it would be impossible to pass in a missing value without an error before even trying to run anything. The various devices you would need to test. But then again, each part (button or image layout and button text) could be tested first on their own. Building high quality parts that you can trust to do the right thing pay for themselves over time and then some. If this doesn't make sense to you, perhaps you should invest in better frameworks, languages, or tooling. Otherwise follow the advice of other comments to try to effectively limit your effort.