Uni Test for Log in Page giving null

i am writing a unitest for login in my project .

when i call the login function of my controller. Memership.GetUser giving null value for passed User. below is Test case

[TestMethod]
    public void Login()
    {

        //Arrange
        AccountController account = new AccountController(_forgotPasswordTokensRepo, _IMessageTemplateDAO, _IEmailService, _ISettingDAO, _IProfileDAO);
        List<AccountBO> TestUsers = new List<AccountBO>();

        AccountBO objAccountBO = new AccountBO();
        objAccountBO.Email = "uu@yopmail.com";
        objAccountBO.Password = "123456789";


        TestUsers.Add(objAccountBO);

        var result = (JsonResult)account.Login(TestUsers[0]);
        var json = new System.Web.Script.Serialization.JavaScriptSerializer();

        string data = result.Data.ToString().Split('=')[1].Trim();
        bool Processdata = Convert.ToBoolean(data.Replace('}', ' ').Trim());

        Assert.AreEqual<bool>(true, Processdata);



    }

Controller function is

public JsonResult Login(AccountBO account, string returnUrl = "")

    {

        bool hasBeenUnlocked = false;
        if (ModelState.IsValid)
        {
           MembershipUser adminUser;
           adminUser = Membership.GetUser(account.Email);
           ------so on
       }

    }

here adminUser = Membership.GetUser(account.Email) is giving null.