In an ideal world one might argue that everything testing-worthy (ie. the logic-heavy parts) is already factored out from the UI components but getting to that point either needs a good amount of foresight and discipline or some a lot of refactoring which is difficult to trust without existing UI tests...
In an ideal world one might argue that everything testing-worthy (ie. the logic-heavy parts) is already factored out from the UI components but getting to that point either needs a good amount of foresight and discipline or some a lot of refactoring which is difficult to trust without existing UI tests...