Unit Test returning null for results, but I can see them in debugger. : The Official Microsoft ASP.NET Forums

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smiller781

Member

172 Points

199 Posts

Unit Test returning null for results, but I can see them in debugger.

Jun 16, 2012 02:50 PM|LINK

I am following along with the SportsStore application in Apress' Pro ASP.Net MVC 3 Framework.

This is a very simple example with a very simple Unit Test.

Here is the controller:
/////////////////////////////////////////////

public class ProductController : Controller
{
	public int PageSize = 4; // We will change this later
	private IProductRepository repository;

	public ProductController(IProductRepository productRepository)
	{
		repository = productRepository;
	}

	public ViewResult List(int page = 1)
	{
		return View(repository.Products
		.OrderBy(p => p.ProductID)
		.Skip((page - 1) * PageSize)
		.Take(PageSize));
	}
}
/////////////////////////////////////////////

Here is the Unit Test
////////////////////////////////////////

[TestMethod]
public void Can_Pagninate()
{
	// Arrage
	Mock<IProductRepository> mock = new Mock<IProductRepository>();
	mock.Setup(m => m.Products).Returns(new Product[] {
		new Product { ProductID = 1, Name = "P1" },
		new Product { ProductID = 1, Name = "P2" },
		new Product { ProductID = 1, Name = "P3" },
		new Product { ProductID = 1, Name = "P4" },
		new Product { ProductID = 1, Name = "P5" },
	}.AsQueryable());

	// Create a  and make the page size 3 items
	ProductController controller = new ProductController(mock.Object);
	controller.PageSize = 3;

	// Action
	IEnumerable<Product> result = (IEnumerable<Product>)controller.List(2).Model;

	// Assert
	Product[] prodArray = result.ToArray();
	Assert.IsTrue(prodArray.Length == 2);
	Assert.AreEqual(prodArray[0].Name, "P4");
	Assert.AreEqual(prodArray[1].Name, "P5");

}

//////////////////////////////////////////////////////////////

The assert is failing with the exception:
Test method SportsStore.UnitTests.ProductControllerTests.Can_Pagninate threw exception: System.ArgumentNullException: Value cannot be null. Parameter name: source

Here is the wierd thing.
If I place a break point here: IEnumerable<Product> result = (IEnumerable<Product>)controller.List(2).Model;

I see this,
controller.List(2).Model
base
Non-Public members
Results View

[0]

Name "P4" ProductID "1"

[1]

Name "P5" ProductID "1"

But when I continue on and finish the test, result gets assinged null and it crashes.
Why is the model returning null to result in:
IEnumerable<Product> result = (IEnumerable<Product>)controller.List(2).Model;

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CPrakash82

All-Star

18284 Points

2841 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Jun 16, 2012 06:24 PM|LINK

Change few lines in your unit test method, like below,

var result = controller.List(2);

//assert

var viewresult = Assert.IsType<ViewResult>(result); Assert.NotNull(result.ViewData.Model);

IEnumerable<Product> productResult = (IEnumerable<Product>)result.ViewData.Model;

Thanks,

http://cprakash.com

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smiller781

Member

172 Points

199 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Jun 17, 2012 02:10 PM|LINK

Thanks but I am using Visual Studio Test Tools.

I don't think Assert has the IsType<T> method.

But I used Assert.IsNotNull(result.ViewData.Model) and it fails because the Model in inline code returns null.
But as I said, if I put a break point and inspect the result, I can hover over and inspect it and open the results of the LINQ query and see all the data, so I don't understand why these lines fail:

Product[] prodArray = result.ToArray();
Assert.IsTrue(prodArray.Length == 2)
Assert.AreEqual(prodArray[0].Name, "P4")

And why it thinks result is null when I can see the results in the debugger watch window.
It's rediculous.

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smiller781

Member

172 Points

199 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Jun 18, 2012 02:59 PM|LINK

So I think the problem is that the reultis a LINQ Query:

- controller.List(2).Model {SportsStore.Domain.Entities.Product[].OrderBy(p => p.ProductID).Skip(3).Take(3)} object {System.Linq.EnumerableQuery<SportsStore.Domain.Entities.Product>}

It just won't execute in real time for the UNIT TEST but exicutes in the watch window.

Man, what is missing here?

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CPrakash82

All-Star

18284 Points

2841 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Jun 19, 2012 01:06 AM|LINK

Linq works in deffered execution, can you try doing F11 and step into controller's List method at this line and see what it is doing?

controller.List(2)

I am not sure why it is happending debugging might help, otherwise I see no reason, why your linq not executes.

Thanks,

http://cprakash.com

Marked as answer by Young Yang - MSFT on Jun 25, 2012 12:37 PM

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dhanekula

Member

101 Points

37 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Jun 19, 2012 01:38 AM|LINK

I Tried it by running in VS. Can you please Try it in your by copying the exact code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace MvcApplication4.Controllers
{
    public class ProductController : Controller
    {
        public int PageSize = 4; // We will change this later
        private IProductRepository repository;

        public ProductController(IProductRepository productRepository)
        {
            repository = productRepository;
        }

        public ViewResult List(int page = 1)
        {
            return View(repository.Products.OrderBy(p => p.ProductId)
            .Skip((page - 1) * PageSize)
            .Take(PageSize));
        }
    }

    public interface IProductRepository
    {
        IEnumerable<Products> Products { get; set; }
    }

    public class Products
    {
        public int ProductId;
        public string Name;
    }
}


UnitTest

 [TestMethod]
        public void Can_Pagninate()
        {
            // Arrage
            

            Mock<IProductRepository> mock = new Mock<IProductRepository>();
            mock.Setup(m => m.Products).Returns(new Products[] {
                new Products { ProductId = 1, Name = "P1" },
                new Products { ProductId = 1, Name = "P2" },
                new Products { ProductId = 1, Name = "P3" },
                new Products { ProductId = 1, Name = "P4" },
                new Products { ProductId = 1, Name = "P5" },
        }.AsQueryable());

            // Create a  and make the page size 3 items
            ProductController controller = new ProductController(mock.Object);
            controller.PageSize = 3;

            // Action
            IEnumerable<Products> result = (IEnumerable<Products>)controller.List(2).Model;

            // Assert
            Products[] prodArray = result.ToArray();
            Assert.IsTrue(prodArray.Length == 2);
            Assert.AreEqual(prodArray[0].Name, "P4");
            Assert.AreEqual(prodArray[1].Name, "P5");

        }

View

@model IEnumerable<MvcApplication4.Controllers.Products>

@{
ViewBag.Title = "title";
Layout = "_Layout";
}

<h2>title</h2>

Dhanekula

Marked as answer by Young Yang - MSFT on Jun 25, 2012 12:37 PM

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SnowFox108

Member

4 Points

2 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Nov 26, 2012 01:15 AM|LINK

This is Error of book

IEnumerable<Product> result = (IEnumerable<Product>)controller.List(2).Model;

// results in an invalid cast exception. The line should read:

IEnumerable<Prodcut> result = ((ProductsListViewModel)controller.List(2).Model).Products;

ProductListViewModel wasn't created at time when you read the book. Just skip this part and later you will create it by following the book.

Reply

SnowFox108

Member

4 Points

2 Posts

Re: Unit Test returning null for results, but I can see them in debugger.

Dec 04, 2012 01:32 AM|LINK

After few days struggle on this, I didn't find any answer throughout the internet. Finally I got the reason. The book's code is correct. The reason of this happened to my situation was. I used different version of Syste.Web.Mvc in my Web project (v3) and UnitTest project (v4). This doesn’t cause error at runtime just doesn’t return ActionResult or ViewResult due to incompatibility.

I wish no one else would waste time on same issue I had.