Application variables unit testing using Moq

I am trying to store application variables in my unit test using moq.

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

This is still not working for me, it doesn't use the application variables.

BTW I am following this link: ASP.NET MVC: Unit testing session variables does't change