design business class for unit test

Question

I'm trying to clean my code to make it unit-testable. I know that unit tests must be created while coding but... I have to do it now, with code completed.

My business class is full of methods with a similar implementation like:

var rep=new NHrepository<ModelClass1>(Session);
rep.Where(x=>x.Field1==1).ToList();

first error (from my point of view) is that I don't have to use "new" but instead use DI and add in the ctor parameters a INHrepository modelClass1Repository.

If in my class I have two or more repository of different model class? Each must be in the ctor? Or probably business class is not build with SeparationOfConcern principle?

Answer 1

You're right about the dependecy injection.

Also, I strongly recommend that you read Working Effectively with Legacy Code if you plan to write unit tests for your legacy code.

Answer 2

One widely used approach is to have n repositories as parameters to your constructors as you already suspected

Another commonly used approach is to use a dependency injection framework such as Ninject. This allows you to write things like:

[Inject]
public IAbstractRepository<Company> companiesRepository { get; private set; }

[Inject]
public IAbstractRepository<User> usersRepository { get; private set; }

You can then have Ninject inject the appropriate implementation of your interface depending on the usage scenario (e.g. a fake repository for testing or a real repository for production)

Answer 3

Your business class should have a contructor with 2 parameters, one for each repository. Your business should expose 2 interfaces, and your persistence should provide their implementations.