JustMock calling ToString() on class that overrides ToString(), Throws null ref

[Keenan]

I have a class that overrides the ToString() method and returns part of a value thats set in the constructor of the class. When attempting to mock this class, JustMock ObjectValue calls the ToString() method before the UserInfo class constructor has run. In this case a null ref exception is thrown. 

        public string FullName => StringHelper.Format("User: '{0}'.", this.User.FullName); 

        public UserInfo(User author)
        {
            this.User = author
        }

        public override string ToString()
        {
            return this.FullName;
        }

Below is the JustMock code

public ObjectValue(Tuple<Type, object> objectDesc)
{
	AssemblyQualifiedName = objectDesc.Item1.AssemblyQualifiedName;
	if (objectDesc.Item2 != null)
	{
		if (objectDesc.Item1.IsValueType)
		{
			StringValue = string.Format((objectDesc.Item1 == typeof(char)) ? "'{0}'" : "{0}", objectDesc.Item2);
		}
		else
		{
			StringValue = string.Format((objectDesc.Item1 == typeof(string)) ? "\"{0}\"" : "{{{0}}}", objectDesc.Item2);
		}
	}
	else
	{
		StringValue = "<null>";
	}
}

I've tried mocking the class but the ToString() method gets called before you can actually mock the method

//Arrange
this.userInfo= Mock.Create<UserInfo>(user);
Mock.Arrange(() => this.userInfo.ToString()).Returns("FullName");

Is there anyway around this?

[Ivo]

Hello Keenan,

I have made a minimal sample project (see attached) using the provided code and some assumptions, but I could not observe such an issue, probably I do not fully understand the idea behind. Could you please modify the project so it could reproduce the problem. Once we have a reproducible scenario we can start looking at it for potential issues.

Regards,
Ivo
Progress Telerik

[Keenan]

Hey Ivo,

Sorry I missed an important part and replicated it with your solution. I added another class that UserInfo Implements

namespace MyClassLibrary
{
    public abstract class DbEntity
    {
        public abstract string HeldName { get; }
    }
}

namespace MyClassLibrary
{
    public class UserInfo : DbEntity
    {
        public string FullName => StringHelper.Format("User: '{0}'.", this.User.FullName);

        public override string HeldName => "user-info";

        public readonly User User;

        public UserInfo(User author)
        {
            this.User = author;
        }

        public override string ToString()
        {
            return this.FullName;
        }
    }
}

[Ivo]

Hello Keenan, I am still unable to figure out what the method ObjectValue is and how it fits in the whole picture, please provide a sample code.

[Keenan]

Ivo,

ObjectValue is a Telerik class in the call stack that is calling ToString() on the base class.  Run the attached solution and view the stack trace. 

[Ivo]

Hello Keenan, it is clear now, I had to check the JustMock code first instead of asking dumb questions, anyway. The issue is related to the DebugWindow feature, so let us try disabling it (on the picture below) and see whether it fixes the problem.

[Keenan]

Hey Ivo,

 

That appears to prevent the issue. Is there anyway around this without disabling it? Not sure what functionality we'll be losing disabling it. 

[Ivo]

Hello Keenan, DebugWindow allows getting a closer look at what is going on inside the framework and it is completely safe to disable it without losing anything from the core functionality. Regarding the possibility of workaround in another way I am afraid there is no simple way to do so.