Don't miss the 'U' in 'GUI'
I mean: if what you're trying to test is all works right and works as it was planned to work, then you may follow Seb Rose's answer.
But please, don't forget a USER interface has to be made thinking about USERS, and not ANY user but the TARGET USER the application was made for. So, after you are sure all works like it have to work, put every single view/screen/form in a test with a team made of users representing every group of different users that may use your application: advanced users, administrators, MS Office users, low computer profile users, high computer profile users... and then, get the critiques of every user, make a mix, re-touch your GUI if it's neccesary and back again to GUI user's test.
