How are you able to Unit Test your controllers without an IoC container?

asp.net-mvc, controller, inversion-of-control, ioc-container, unit-testing

Solution

Isn't it possible to keep the direct instantiation of the field and also provide the setter? In this case you'd only be calling the setter during unit testing. Something like this:

public class QuestionsController : ControllerBase
{
    private IQuestionsRepository _repository = new SqlQuestionsRepository();

    // Really only called during unit testing...
    public QuestionsController(IQuestionsRepository repository)
    {
        _repository = repository;
    }
}

I'm not too familiar with .NET but as a side note in Java this is a common way to refactor existing code to improve the testability. I.E., if you have classes that are already in use and need to modify them so as to improve code coverage without breaking existing functionality.

Our team has done this before, and usually we set the visibility of the setter to package-private and keep the package of the test class the same so that it can call the setter.

Problem

I'm starting to get into Unit Testing, Dependancy Injection and all that jazz while constructing my latest ASP.NET MVC project. I'm to the point now where I would like to Unit Test my Controllers and I'm having difficulty figuring out how to appropriately do this without an IoC container. Take for example a simple controller: ``` public class QuestionsController : ControllerBase { private IQuestionsRepository _repository = new SqlQuestionsRepository(); // ... Continue with various controller actions } ``` This class is not very unit testable because of its direct instantiation of SqlQuestionsRepository. So, lets go down the Dependancy Injection route and do: ``` public class QuestionsController : ControllerBase { private IQuestionsRepository _repository; public QuestionsController(IQuestionsRepository repository) { _repository = repository; } } ``` This seems better. I can now easily write unit tests with a mock IQuestionsRepository. However, what is going to instantiate the controller now? Somewhere further up the call chain SqlQuestionRepository is going to have to be instantiated. It seems as through I've simply shifted the problem elsewhere, not gotten rid of it. Now, I know this is a good example of where an IoC container can help you by wiring up the Controllers dependancies for me while at the same time keeping my controller easily unit testable. My question is, how is one suppose to do unit testing on things of this nature without an IoC container? Note: I'm not opposed to IoC containers, and I'll likely go down that road soon. However, I'm curious what the alternative is for people who don't use them.

Original source