Moq Application variables

This is the first time I am using moq and cannot really find a good tutorial on how to use it for application variables. I in my controller i am calling a method that calls HttpContext.Current.Application["TheConnectionString"] and im my global.asax I declared and initialized Application["TheConnectionString"] = "MyConnectionString"

[TestMethod]
public void TestGetCompanyList()
{
    string applicationValue = "MyConnectionString";
    var mockApplication = new Mock<HttpApplicationStateBase>();
    mockApplication.SetupSet(s => s["TheConnectionString"] = It.IsAny<string>()).Callback((string name) => applicationValue = (string)val);
    mockApplication.SetupGet(s => s["TheconnectionString"]).Returns(() => applicationValue);

    var request = new Mock<HttpRequestBase>();
    var context = new Mock<HttpContextBase>();

    request.SetupGet(x => x.Headers).Returns(new System.Net.WebHeaderCollection {{"X-Requested-With", "XMLHttpRequest"}});
    context.SetupGet(ctx => ctx.Request).Returns(request.Object);
    context.SetupGet(x => x.Application).Returns(applicationValue);


    var accController = new AccSerController();
    CInt cInt = new CInt();
    cIn.Iss = "Other";
    cIn.Tick = "BK";
    var result = accController.GetClist(cIn) as IEnumerable<CList>;
    Assert.IsNotNull(result);
}

I dont know how to "connect" the application value to the controller.