ASP.Net Looking for guidance how to unit test code for MVC action

Question

apologized to post this question here but i am in problem suddenly because i need to write unit test code for action where i am not good.

i am bit familiar with asp.net mvc. before i never write unit test code for action rather i manually test the action. now i want to know the art of writing unit test code for my action. so i read couple of article on unit test but notice all article share very basic idea about to write unit test code for action method in mvc controller but i am not being able to write unit test code for my action. so here i am pasting my one sample controller and their actions. so anyone please share knowledge how to write unit test code for my action methods below. if possible discuss with code sample or good hint which enable to write unit test code in VS2013 and MVC version 5.

here is my code

public class StudentController : Controller
    {
        private StudentRepository _Studentdata;
        private StateRepository _Statedata;
        private CityRepository _Citydata;

        public StudentController()
        {

            _Studentdata = new StudentRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentDBContext"].ConnectionString);
            _Statedata = new StateRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentDBContext"].ConnectionString);
            _Citydata = new CityRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentDBContext"].ConnectionString);

            //_Studentdata = new StudentRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentSQLDBContext"].ConnectionString);
            //_Statedata = new StateRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentSQLDBContext"].ConnectionString);
            //_Citydata = new CityRepository(System.Configuration.ConfigurationManager.ConnectionStrings["StudentSQLDBContext"].ConnectionString);

        }

        // GET: Stuent
        public ActionResult List(StudentListViewModel oSVm)
        {
            if (Request.IsAjaxRequest())
                System.Threading.Thread.Sleep(1000); // just simulate delay of one second

            StudentListViewModel SVm = new StudentListViewModel();
            SVm.SetUpParams(oSVm);
            SVm.Students = _Studentdata.GetStudents(oSVm.page, oSVm.PageSize, oSVm.sort, oSVm.sortdir).ToList();
            SVm.States = _Statedata.GetAll().ToList();
            SVm.Cities = _Citydata.GetAll().ToList();
            SVm.RowCount = _Studentdata.DataCounter;
            return View("ListStudents",SVm);
        }

        [HttpPost]
        public ActionResult UpdateStudents(StudentListViewModel oSVm, string Action)
        {
            if (Request.IsAjaxRequest())
                System.Threading.Thread.Sleep(1000); // just simulate delay of one second

            StudentListViewModel SVm = new StudentListViewModel();
            SVm.SetUpParams(oSVm);
            if (Action == "UPDATE")
            {
                SVm.Students = _Studentdata.SaveXML(new List<Student>(oSVm.Students).ToXml("Students"),
                    oSVm.page, oSVm.PageSize, oSVm.sort, oSVm.sortdir).ToList();
            }
            else if (Action == "DELETE")
            {
                SVm.Students = _Studentdata.Delete(oSVm.Students[0].ID,
                    oSVm.page, oSVm.PageSize, oSVm.sort, oSVm.sortdir).ToList();

            }

            SVm.States = _Statedata.GetAll().ToList();
            SVm.Cities = _Citydata.GetAll().ToList();
            SVm.RowCount = _Studentdata.DataCounter;
            return PartialView("_StudentGrid", SVm);
        }

        [HttpPost]
        public ActionResult RefreshStudents(StudentListViewModel oSVm)
        {
            if (Request.IsAjaxRequest())
                System.Threading.Thread.Sleep(1000); // just simulate delay of one second

            StudentListViewModel SVm = new StudentListViewModel();
            SVm.SetUpParams(oSVm);
            SVm.Students = _Studentdata.GetStudents(oSVm.page, oSVm.PageSize, oSVm.sort, oSVm.sortdir).ToList();
            SVm.States = _Statedata.GetAll().ToList();
            SVm.Cities = _Citydata.GetAll().ToList();
            SVm.RowCount = _Studentdata.DataCounter;
            return PartialView("_StudentGrid", SVm);
        }

        [HttpGet]
        public JsonResult GetCityName(int StateID)
        {
            if (Request.IsAjaxRequest())
                System.Threading.Thread.Sleep(1000); // just simulate delay of one second

            return Json(new {CityList =_Citydata.GetCityByStateId(StateID)} , JsonRequestBehavior.AllowGet);
        }

    }

Thanks