Hopefully, you've separated out the logic of manipulating some data and performing an action upon it, from the layer. Your unit tests should be as simple as possible, and not dealing w/ your web layer - your presentation layer. It makes your tests simpler w/o debugging the html, the presentation layer AND the business layer.

It sounds like what you are talking about is interface testing, or end to end testing. Unit testing programmatically will be a bitch. What's worse is, you won't be testing the layout, the JS involved, form elements rendering - text area instead text field, radio button instead of checkboxes. There are tools, though I don't know them off the top of my head, to make IE and Firefox emulate a user browsing around. Something like, http://www.worksoft.com/ContentDisplay/G11/G11L60.asp, though I have no clue of the quality of that particular piece. Just an example of what you should look for.