Question

We have a bug to fix, and like any good TDD practitioner, I want to write a failing test to represent the bug first. The bug is in a method that takes a rather complex type as input. The bug will only reproduce when the complex type has a certain combination of property values set.

So far I have reproduced the bug and, in the debugger, can view the run-time value of the complex type. Now I need to create that complex type in the “Arrange” section of my unit test so that I can feed it to the buggy method in the “Act” section of the unit test.

I can write a big object initializer code block, by hand, such as the following one:

var cats =
    new List<Cat>
        {
            new Cat {Name = "Sylvester", Age = 8},
            new Cat {Name = "Whiskers", Age = 2}
        };

or even something like this:

var cats = new List<Cat>();
var cat1 = new Cat();
cat1.Name = "Sylvester";
cat1.Age = 8;
cats.Add(cat1);
var cat2 = new Cat();
cat2.Name = "Whiskers";
cat2.Age = 2;
cats.Add(cat2);

Nothing fancy there. The only problem is the “by hand” part — the complex type in my case is not nearly as trivial as the above example.

I can also view the object, while in the debugger, with any of the built-in debugger visualizers. So I figured I would write a custom Debugger Visualizer that will generate the object initialization code for me. To use it, I would reproduce the issue in the debugger, pull up the QuickWatch window and select my custom visualizer.

Another option would be to write a custom serialization implementation that would “serialize” to a block of object initialization code. To use this would be a bit harder than just pulling up the QuickWatch window, but this could work.

Before I tackle this problem myself, has anybody done something like this? Mind sharing a code snippet? Or would anyone suggest another approach?

P.S. In my case, the type of the object is a subclass of an abstract base class. Just wanted to mention it.

Answer 1

These suggestions aren’t going to work. Read the first line:

You can write a custom visualizer for
an object of any managed class except
for Object or Array.

http://msdn.microsoft.com/en-us/library/e2zc529c.aspx

There is your answer. If I’m reading correctly it can’t be implemented through a visualizer. Sort of lame.