Mocking out a local variable in C#

Question

I have a C# class which instantiates on its own a NetworkCommunicator class. I'd like to mock out the NetworkCommunicator class for my unit test, and replace it with a pretty simple stub.

But the NetworkCommunicator is never passed as a parameter. It's created by the class being tested.

In Ruby, this is easy to mock out. In Java, this is why you need Dependency Injection, which is too heavy for this project. Is there a simple way to mock this out in C#, perhaps using Moq or something similar?

Answer 1

You mentioned that DI is too heavyweight for this project, why not try some Truck Driver's DI, thus:

public interface IDependency
{
    void DoSomeStuff();
}

public class ClassUnderTest
{
    private IDependency _dependency;

    public ClassUnderTest(IDependency dependency)
    {
        _dependency = dependency;
    }

    public ClassUnderTest() : this(new Dependency())
    {}

    public void ImportantStuff()
    {
        _dependency.DoSomeStuff();
    }
}

Using this constructor chaining technique, you can now mock the IDependency all you want, without worrying about hooking up DI or IoC.