Download the sample project and source for this post: xUnit-Light with SubSpec

One of the sessions I attended at the Utah Code Camp was “Behavior Driven Development and Executable Specifications in .NET” by David Starr.  This pumped me up to look at BDD again.  I recalled seeing an example of SubSpec for xUnit, though currently the full version of xUnit is desktop only.  So I set out to make the prototype of SubSpec run in Silverlight!  I started from the xUnit-Light built by Jason Jarrett.  I added two classes, ActionTestMethod and ExceptionTestMethod, then altered the TestClass, which was already looking for Fact attributes, to look for Specification attributes as well.

Here’s an excerpt from the code in TestClass.cs that generates the available test methods:

ICollection specMethods =
	GetMethodsWithAttribute(_type, typeof(SpecificationAttribute));

_tests = new List(specMethods.Count);
foreach (MethodInfo method in specMethods)
{
	try
	{
		object obj = Activator.CreateInstance(method.ReflectedType);
		method.Invoke(obj, null);

		var tests = SpecificationContext.ToTestCommands(method);

		foreach (var test in tests)
		{
			_tests.Add(test);
		}
	}
	catch (Exception ex)
	{
		_tests.Add(new ExceptionTestMethod("GetTestMethods()", ex));
	}
}

And here’s a sample test:

[Specification]
public void PushNullSpecifications()
{
  Stack stack = null;

  "Given a new stack".Context(() => stack = new Stack());

  "with null pushed into it".Do(() => stack.Push(null));

  "the stack is not empty".Assert(() => Assert.False(stack.IsEmpty));
  "the popped value is null".Assert(() => Assert.Null(stack.Pop()));
  "Top returns null".Assert(() => Assert.Null(stack.Top));
}

Which runs the tests:

Given a new stack with null pushed into it, the stack is not empty
Given a new stack with null pushed into it, the popped value is null
Given a new stack with null pushed into it, Top returns null

There’s quite a bit of debate around using this type of syntax on Phil’s post introducing SubSpec, and as I start to create more BDD style tests I may end up agreeing with some of the comments.  Though right now this works great for me.  Johannes Rudolph has also started a new project based on the SubSpec sample which has a few more features.  You can grab the sample project and source code from this post here.