I am supposed to be using test-driven development but in this particular case, as I am having trouble, I implemented the action method first. It looks like this:

public ViewResult Index(int pageNumber = 1)
{
    var posts = repository.All();
    var model = new PagedList<Post>(posts, pageNumber, PageSize);

    return View(model);
}

Both the repository and the PagedList<> have been tested already. Now I want to verify that when the action is given a page number that the page number is actually considered.

private Mock<IPostsRepository> repository;
private HomeController controller;

[Test]
public void Index_Doohickey()
{
    var actual = controller.Index(2);

    // .. How do I test that the controller actually uses the page number here?
}