What about Views?
Erm, Selenium and WatiN.
Really, what makes you think that ASP.NET MVC views are any different than classic ASP.NET WebForms as far as integration tests are concerned? I mean they all spit HTML at the end of the day. That's what browsers and stuff like Selenium understand. Who spit this HTML is not that much important. What you care about in an integration test is that when a user lambda clicks on a button alpha after entering beta in the gamma text field hi got this Welcome User Phi
on the resulting HTML page, don't you? You really don't care about things like ASP.NET MVC or even less about things like ASP.NET MVC Views.
By the way you could use Selenium and WatiN with PHP. Or with Java Servlets if you are a fan of them. Doesn't really matter the server side technology you are using. What matters in an integration test is the scenarios that you have defined previously.
If so, what would be the difference between WebTesting in WebForms and WebTesting in MVC?
None.