Modelstate.AddModelError Object reference not set to an instance of an object error

Question

User-501297529 posted

I get this error during unit testing. 

Test::

 public void EditItemStatus_Post_HandlesNotValid()
        {
            //arrange
            var createEditItemStatusViewModel = new CreateEditItemStatusViewModel()
            {
                Name = "Test",
                ColorId = 5,
                ItemStatusId = 4
            };
           
            _controller.ModelState.AddModelError("Error", "Error");
            var result = _controller.EditItemStatus(createEditItemStatusViewModel) as ViewResult;

            //assert
            Assert.That(result, Is.Not.Null.And.InstanceOf<ViewResult>());
            _mockService.VerifyAll();
            _mockService
                .Verify(p => p.CreateEditStatus(It.IsAny<ItemStatus>()), Times.Never, "The Status could not be saved at this time");
        }

Post Action:

 public IActionResult EditDorItemStatus(CreateEditDorItemStatusViewModel StatusToEdit)
        {
            var availableColors = _service.GetAvailableColors().ToList();
            availableColors.Add(new StatusColor() { ColorId = 0 });
            StatusToEdit.AvailableColors = new SelectList(availableColors, "ColorId", "Name", availableColors.FirstOrDefault(c => c.ColorId == StatusToEdit.ColorId)?.ColorId);
            

            if (ModelState.IsValid)
            {
               
                
                var statusToBeEdited = _service.GetStatus(StatusToEdit.ItemStatusId);

                // Checks if item to be edit is null
                if (statusToBeEdited == null)
                {
                    ModelState.AddModelError("StatusNotFound", "A matching item cannot be found to edit.");
                    return View(StatusToEdit);
                }
               
                
                try
                {
                    _mapper.Map(dorStatusToEdit, statusToBeEdited);
                    
                    if (_service.CreateEditStatus(statusToBeEdited))
                    {
                        ViewData["SuccessMessage"] = "Changes to the Status have been successfully saved.";
                        return View(StatusToEdit);
                    }
                    
                    ModelState.AddModelError("UpdateFailure", "Submitted status contained invalid values. ");
                    return View(StatusToEdit);

                }
                catch
                {
                    
                    ModelState.AddModelError("UpdateFailure", "The status could not be saved at this time.");
                    return View(StatusToEdit);
                }
               
            }
            return View(StatusToEdit);
        }

Not sure what I'm missing and why it errors on that line.

Answer 1

User-474980206 posted

where did you construct the controller?

Answer 2

User-501297529 posted

where did you construct the controller?

Not sure what you mean? Do you mean constructors?

Answer 3

User475983607 posted

Where are you creating _controller?

_controller.ModelState.AddModelError("Error", "Error");

Testing controllers is cover at the following link which might help.

https://docs.microsoft.com/en-us/aspnet/core/mvc/controllers/testing?view=aspnetcore-2.2

Answer 4

User-501297529 posted

I'm creating _controller in the Test class file. Not sure if this helps.

Unit test code:

 internal class ControllerTest
    {
        #region Test Resources

      
        private Controller _controller;
       
}

This is controller code:

public class Controller : AdminControllerBase
    {
       

        public Controller(IService Service)
        {
            _service = Service;
            
        }
}

Answer 5

User475983607 posted

You created a controller reference...

private Controller _controller;

but have not show where you "new" up a controller type.  Which would look somehting like....

_controller = new ControllerUnderTest();

I recommend going through the link in my previous post which illustrates how to test controllers.

Answer 6

User-501297529 posted

I figured this one out. I need to call the controller in the test method:

_controller = new Controller(_mockService.Object, _mockNewItemStatusMapper.Object);