If the framework you're using allows for ui testing, you must use it. For example in flutter, you can check whether a component is visible on the "screen" and

If the framework you're using allows for ui testing, you must use it. For example in flutter, you can check whether a component is visible on the "screen" and simulate an action with it. No need to ask a human to test the new ui if you can detect that the new button isn't visible on the "screen" . Then once you know what's supposed to be there is there, a human must test it.