While working on PlanningPokerOnRails I started writing a unit test for my LoginController. The Monorail BaseControllerTest makes this easy. I am also using Rhino Mocks and Nunit. Here is the test:
The test is very simple. First, it sets a single recorded expectation that a Redirect will occur:
34 using (mocks.Record())
35 {
36 // First redirects to the index page
37 Response.Redirect("/Home/Index.rails");
38 }
Next, the playback is run and the code emulates a few things that users might do...like login with Request params for a ReturnUrl:
39 using (mocks.Playback())
40 {
41 Request.Params.Add("ReturnUrl", "/Home/Index.rails");
42 loginController.Login("dan", "danny");
43 }
Writing the Code to Pass this Test
Next I wrote the CardPlayer component (my user) and the LoginController. Seeking to do the simplest thing that could possibly work I merely had the CardPlayer inherit from the ActiveRecord base.
This made writing the controller easy, the ActiveRecord base has plenty of good methods for instantiating. I only have to call the FindOne method on the CardPlayer:
104 public static CardPlayer FindCardPlayer(string UserName,
105 string Password){
106
107 CardPlayer user = FindOne(NHibernate.Expression.Expression.And(
108 Expression.Eq("Username", UserName),
109 Expression.Eq("Password", Password)));
110 return user;
111 }
So why all the Problems?
I never intended to initialize ActiveRecord, in my tests assembly. I believe that test data should only be used for Acceptance Tests. It turns out that the test fails because no ActiveRecord config or initialization exists.
How do I solve this?
I forgot to implement good Dependency Injection. The way I would normally grab an instance of a component (like the CardPlayer) is through a service container (or repository). MVC architectures generally have two types of Model objects; Components (like the CardPlayer) and Services (like the CardPlayer Service I should have written). The services usually act like or wrap a repository of Components. In my opinion, ActiveReecord already provides the repository.
It turns out my solution is to write a CardPlayer Service container. This object will go into the IoC container (winsor) and be automatically injected into whatever controller requires it (like the LoginController). The service will use the ActiveRecordMediator to instantiate new CardPlayers and I can remove the ActiveRecordBase from my CardPlayer component.
Wait why does this help?
Well by forcing all instantiation to go through injected Services your tests can easily inject a Mock Service (I use Rhino Mocks) and tell the Mock to provide predefined instances of components. Since you have mocked the service layer you no longer need ActiveRecord in your tests!
Keeping the Data
Now that I've convinced you to write a service layer, I am going to tell you that you may not need it! While you can mock the Services going to your controllers you cannot easily get rid of ActiveRecord when testing the services. For most simple lookups a test may not be appropriate but in many cases your component lookup up and other operations will be non-trivial. For these cases you will want to test the service layer and you may have to initialize ActiveRecord.
You could decide to Mock the ActiveRecordMediator or you could use an approach similar to Oren's.
I'm Confused...
I admit that this is some advanced stuff. I promise to come back to this post and update it with more concise information.
Please leave comments on ways I can do this without a service layer. Thanks!
