Most people who write UIs don’t care about testing. You know why? Because it’s hard. So hard, they’d rather not even bother and test things manually. You have multiple browsers. You have multiple platforms. And worse, you have all these frameworks and toolkits which are difficult to test. I’ll pick on GWT here for a moment. It takes 20 seconds to start a test – let alone a server side component to interact with or the time it takes to run your test.