The following article is excellent in explaining in detail all the tests that you should write when testing controllers, including when to use a mocking framework. It is also short too. http://www.arrangeactassert.com/how-to-unit-test-asp-net-mvc-controllers/
Excerpt from the article:
Let me start off by discussing what types of unit tests you should be creating for MVC controllers. Tests to check the correct action result is returned from a controller action. This includes information about the action result, such as the testing the correct view is returned for a view result.
Tests to check if the view model is what you expected. If you have a strongly typed view which expects class foo and you pass class bar to your view model, your code will compile, would result in a runtime error like the one shown below.
If you are testing anything more than this your controller is doing too much.