Discussion on: Code Smell 135 - Interfaces With just One Realization

[Maxi Contieri]

Thank you very much for the code.

I think the problem is here

"Assume you have a class Car which depends on a class DieselEngine. It would not be possible to write a unit test just for the Car when the concrete type DieselEngine is required from the Car constructor."

Why not test the Car with a DieselEngine ? This is a real business scenario

Also, IMHO , Callling an interface IEngine is another smell. Even dough I know it is a standard practice.
Can I use your code snippet in another smell ?

[Stepan Mozyra]

"Why not test the Car with a DieselEngine ?" - This is idea behind unit tests :) to have a single unit under the test.

If you do unit testing in your project - you will always have two implementations of your interfaces.

"This is a real business scenario" - Testing of business scenarios is just an another kind of tests.

[Maxi Contieri]

Right !

You have two interfaces realizations. Therefore this code smell does not apply anymore

[David Kröll]

Can I use your code snippet in another smell ?

Yes feel free.

It depends on what you call a unit I think, bit you're right. If the DieselEngine is testable at all (could be a real DieselEngine which is not availabe during CI test run, etc).

[Maxi Contieri]

Build your abstractions with TDD so they will be testaable from their inception