Are you new to the concept of code katas? Read my previous blog post and watch me perform the String Calculator Kata.

In my never ending goal of self improvement in the techniques and tools I use I’ve been practicing a version of the Prime Factors Kata for a while.

The Prime Factors Kata, initially sparked by the infamous Uncle Bob Martin, is about finding an arbitrary number’s prime factors. In the cast I show how my TDD practice has evolved into a flavor of BDD, mainly to reduce duplication in the unit tests. I also show off the awesome power of my current toolset which includes the Visual Studio 2010 and the latest versions of ReSharper, TestDriven.NET, NUnit and NBehave.

Though my performance is not yet perfected I want to put it out there because I feel there are no C# version that can really match the Ruby version in elegance and wit. This is my attempt to show what you can do with the C# language when you know the frameworks really well.

Please leave comments and/or suggestions below or record your own kata session in response.

Prime Factors Kata in C# from Rickard Nilsson on Vimeo.

If you are new to the Prime Factors Kata, code katas in general, or TDD for that matter, you may find the steps I take unnecessary or weird. You may want to watch the annotated version in which Uncle Bob explains why each step is taken and why they are taken in that order.

• Uncle Bob’s annotated version

Many have recorded there own versions of the Prime Factors Kata which all inspired me in the way I practice it. The cast that inspired me the most is

• Uncle Bob’s Ruby version

there are also a few other C# casts worth watching for comparison by:

• Uri Lavi
• Slatner

In the following example I will show how easy it is to isolate your client code from ASP.NET code, using the Moles Isolation Framework, in order to test that your code performs as intended.

The example should not be seen as an encouragement to use bad design. On the contrary, I urge you to use Moles to get that ugly, old legacy code you’ve got, and put it under test such that you will have the freedom to rip it apart and improve it.

Prerequisites

1. Download and install Moles Isolation Framework for .NET
2. Open your Solution
3. Create a test project by doing File > Add > New project > Test > Test Project
4. Add the following references
   1. Microsoft.Moles.Framework
      %MolesPath%\PublicAssemblies\Microsoft.Moles.Framework.dll
   2. System.Web
5. On the test project: choose Add > New Item…
6. Choose the Moles template “Moles and Stubs for Testing”
7. Name it “System.Web.moles”

Now Moles will generate an assembly with mocks and stubs of the target assembly (System.Web) and add it to the test project. Your references should look like this:

Class under test

Now you are ready to start writing tests. First we take a look at our sample application. It is a simple ASPX-page which calls Server.MapPath() in the Page_Load method:

In our unit test we want to be able to replace the call to Server.MapPath() such that

1. We won’t get an NullReferenceException
2. We can control what is returned

The following test method will fake the call to Server.MapPath() and assert that it was actually called by the method under test:

Under the covers

To accomplish this we need to understand what is going on. “Server” is an instance property on the System.Web.UI.Page class which eventually will invoke the HttpContext.Current.Server property. Thus, to fake the method call we need to fake several things:

1. Static property HttpContext.Current
2. Instance property Server on HttpContext
3. Instance method MapPath on HttpServerUtility

Access modifier

Finally, to be able to execute the method under test (Page_Load), we need to change its accessibility from protected to public.

Summary

I've shown how easy it is to get started covering your ASP.NET codebehinds with unit tests utilizing Moles Isolation Framework. This article will be followed up with more examples on how to leverage Moles. Please leave feedback and any questions you might have. Good luck testing!

Moles is a new framework from Microsoft Research for isolating objects in unit tests. With the framework you create test stubs by using delegates and you can route any .NET method you want, including non-virtual and static methods in sealed classes. In addition, the framework is free, making it a major competitor to TypeMock Isolator that has been alone on this functionality for a long time.

Moles automatically generates stubs for all classes in one assembly. Here is an example of how easy it is to change the behavior of the static DateTime.Now property:

For SharePoint

Mole’s strength to fake and reroute static methods and the like makes it a very powerful tool for isolating and unit testing code developed for SharePoint. Microsoft Research has a whitepaper that describes how to get started:

Unit Testing SharePoint with Microsoft Foundation Pex and Moles

Introduction

Here is a video that introduces Moles:

Enabling truly easy testability with ASP.NET MVC Controllers requires a Dependency Injection container. This post is about showing a more real life example of combining Unity with ASP.NET MVC Controllers than the standard demo. Unity is the IoC Container from Microsoft Patterns & Practices and ships as a part of Enterprise Library as well as a stand alone on Codeplex.

We start with the unit test which drives the design of the controller.

Even though the test becomes a bit verbose it clearly states the intent of the controller’s Post method; given the right slug, a result is returned with a blog post as model.

Dependency Injection in ASP.NET MVC

In ASP.NET MVC every request starts in a controller which uses a set of dependencies to do its job. When we have applied Inversion of Control we can inject all of the controller’s dependencies either as a constructor argument or as a property setter. To fully take advantage of this technique we want the dependencies to be automatically injected without creating any of them in overloaded constructors or something like that. This is where the Controller Factory in ASP.NET MVC comes into play.

Controller Factory

In the System.Web.Mvc namespace lives the IControllerFactory which implementation is used by the framework to create controller instances. We can use this to swap out the default one and replace it with our own controller factory which uses Unity to create controllers instead.

Instead of implementing all of the IControllerF actory functionallity we can extend the System.Web.Mvc.DefaultControllerFactory and only override what we need.< /p>

In the Global.asax, called MvcApplication in ASP.NET MVC by default, we create our Unity container and tells the MVC framework to use our UnityControllerFactory instead of the default one.

PostController

To illustrate why this is so powerful we will implement a controller that handles requests for blog posts, such as the one you’re reading right now. For this example the controller only handles requests for single blog posts using the post’s slug as identity. A slug is the post’s title made url friendly (e.g. "Dependency-injection-in-ASPNET-MVC-with-Unity-IoC-Container” for this post). The PostController has a dependency on an IBlogPostService which it uses to lookup the blog post to send to the view.

Strongly-typed views

The Post action returns an ActionResult with the post a the model. We can use strongly-typed views to get intellisense in the aspx-file.

<%@ Page /*...*/ Inherits="ViewPage<IBlogPost>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">

    <%=Model.Title %>

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2><%=Model.Title %></h2>

    <p>

        <%=Model.Body %>

    </p>

    <p><%=Html.PostActionLink("Permalink", Model) %></p>

    <p><a href="/2009/10/10/fail">fail link</a></p>

</asp:Content>

Notice how the view inherits from ViewPage<IBlogPost> which is key to make the model type of IBlogPost. Then we can use the Post properties to render the blog post in the view.

Conclusion

Combining ASP.NET MVC with Unity or your IoC Container of choice makes your controllers much more easily testable. You only state your classes dependencies as constructor parameters or properties and the container will do the wiring for you. The gives you time to focus on the program logic and the interaction between its components.

Much of the legacy ASP.NET code I’ve seen is littered with calls to methods on the HttpServerUtility class,

Why, if your suite has thousands of tests and many calls IO or datebases, the tests will run slowly, and the developers on the team won’t run them as often. Ultimately, you may loose your investment in automated testing because it isn’t providing the promised feedback.

• First of all, if the code is in the code behind of an aspx-file we need to extract as much as possible into its own class, which can be newed up in a unit test.
• Second of all, we need to extract all external dependencies of the class such that fakes can be injected.

If the code behind code calls Server.MapPath() it is actually calling the Server property on the Page base class which returns HttpContext.Current.Server. This is an instance of the HttpServerUtility class, which is sealed and thus pretty impossible to fake out*.

Solution

In the namespace System.Web.Abstractions, which is part of ASP.NET 3.5, lives an abstraction of the HttpServerUtility, called HttpServerUtilityBase. It has a concrete implementation named HttpServerUtilityWrapper that takes an HttpServerUtility instance as a constructor parameter, as follows:

By leveraging a simple form of dependency injection we can preserve the old code as a first step of refactoring, and using an overloaded constructor to inject the fake object in our unit test.

Now, in a unit test for the Presenter class we can inject a fake server utility, which won’t call any IO.

Instead of implementing your own fake you can easily use your preferred isolation (mocking) framework of choice.

Conclusion

The goal is to isolate the class under test from all of its dependencies, weather they call IO, a database, a third party component, or even statics or touch static state. The point is that we want to assert that the class under test behaves as expected, not how the underlying framework behaves.

By leveraging the System.Web.Abstractions namespace we can preserve much of the existing ASP.NET code while covering it with tests.

_________
* Unless using TypeMock Isolator