Unit testing Application Variables with Moq without an interface

I am trying to unit test this application that uses application variables. There is no interfaces or virtual methods in the program and I am finding it difficult to make Moq work.

Class that uses Application Variables:

static string Username = HttpContext.Current.Application["Username"].ToString();

It is initialized in the global.asax file.

My Unit test:

[TestMethod]
public void TestGetCompanyList()
{
    Mock<HttpContextBase> context = new Mock<HttpContextBase>();
    Mock<HttpApplication> app = new Mock<HttpApplication>();

    context.Setup(ctx => ctx.ApplicationInstance).Returns(app); //ERROR

    var accountController = new AccountServiceController();

    accountController.ControllerContext = new ControllerContext(context.Object, new RouteData(), accountController); //ERROR


    CompInput cInput = new CompInput();
    cInput.IssuerName = "Addams";
    cInput.Ticker = "AD";
    var result = accountController.CompList(cInput) as IEnumerable<CompListResult>;
    Assert.IsNotNull(result);
}

The first error:

Error 4 The best overloaded method match for Moq.Language.IReturns<System.Web.HttpContextBase,System.Web.HttpApplication>.Returns(System.Web.HttpApplication)' has some invalid arguments

Error 5 Argument 1: cannot convert from 'Moq.Mock<System.Web.HttpApplication>' to 'System.Web.HttpApplication'

Second Error:

Error 6 The best overloaded method match for 'System.Web.Mvc.ControllerContext.ControllerContext(System.Web.HttpContextBase, System.Web.Routing.RouteData, System.Web.Mvc.ControllerBase)' has some invalid arguments

Error 7 Argument 3: cannot convert from 'Stocktrage.Investor.AccountServiceAPI.Controllers.AccountServiceController' to 'System.Web.Mvc.ControllerBase'

This is my first time using Moq (or any mocking tool), so I am not 100% sure if this can be done without interfaces.