Unit Testing and PostSharp

Question

I'm wondering what the best way to do this is... I'm interested in introducing PostSharp into one of my projects, but I'm not sure how to unit test classes marked with an attribute properly.

For example:

public class hello {

    [MyAspectThatDoesSomethingToTheDatabaseWhenThisMethodGetsCalled]
    public int omg(string lol) {
        //fancy logic in here
    }
}

I'd like to test the logic in the omg() method, but in the unit tests I need to make sure that the aspect doesn't get called, because there isn't really a database.

Thoughts?

Answer 1

Probably you can use dependency injection and introduce a static property for the aspect class where you decide which kind of database access provider you will use (e.g. using a factory), setting up the fake one in scope of a test.

Answer 2

My opinion is that you should test the code as if the aspect were coded manually -- i.e. test the full functionality of the method, including the functionalities implemented by the aspect.

Answer 3

I don't agree with Gael. I've learned from a friend that I must test the code that I'm going to write and in general only once.

Answer 4

I'm not entirely sure how postsharp works, but as I currently understand, you invoke a post build process to weave the aspects into the IL.

If my understanding is correct and if you can skip the post-build weaving then you should be testing your method in ignorance of the aspect ( and testing the aspect separately somewhere else ).

Why?

If you test the aspect and the method, you are testing 3 things at once:

1. the method
2. the aspect
3. the weaving of the aspect into the code

This is bad karma and may lead you down the rabbit hole if something goes wrong ( as well as making your unit test into an integration test ).

Looking at the list above:

• you do need to test the method, in isolation with no other distractions as this will let you focus on making sure the method does exactly what you expect - no more, no less.
• you don't need to test the aspect every time it is used, just test it once and make sure it does what you think it does
• you don't need to test that the weaving works; it is ( should be ) tested as part of the post sharp implementation.