How do I Mock User.Identity with MOQ?

Question

I am new to unit testing, and I need to mock the user Identity in my controller. My Test fails at User.Identity.IsAuthenticated. I get a nullReferenceException. I mean this is expected. I believe I just do not know how to use Moq with Identity.

        public IActionResult Index()
        {
            bool isAuthenticated = User.Identity.IsAuthenticated;


            if (!isAuthenticated)
            {
                return RedirectToPage("/Account/Login", new { area = "Identity" });
            }

            var claimsIdentity = (ClaimsIdentity)this.User.Identity;
            var claim = claimsIdentity.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier);



            userId = claim.Value;

            var model = new YeetViewModel();
            location = _accountServices.getLocation(userId);
            model.yeets = _yeetServices.GetYeetsByNew(location);

            model.location = location;

            return View(model);
        }

This is my Test function

 [Fact]
        public void PassWithUser()
        {
            // Arrange


            var controller = new YeetController(_logger);


             var fakeHttpContext = new Mock<HttpContext>();
            var fakeIdentity = new GenericIdentity("User");
            var principal = new GenericPrincipal(fakeIdentity, null);


            ViewResult views = controller.Index() as ViewResult;

            // Act
            // Expecting it to throw because the user inside Index is null and not set to anything
            Assert.NotNull(views);
        }

Please help me understand what I am doing wrong, and how to actually use Moq correctly. Sorry for my beginerness.