How do you override a module/dependency in a unit test with Dagger 2.0?

Question

I have a simple Android activity with a single dependency. I inject the dependency into the activity\'s onCreate like this:

Dagger_HelloComponen         


        

Answer 1

THIS ANSWER IS OBSOLETE. READ BELOW IN EDIT.

Disappointingly enough, you cannot extend from a Module, or you'll get the following compilation error:

Error:(24, 21) error: @Provides methods may not override another method.
Overrides: Provides 
    retrofit.Endpoint hu.mycompany.injection.modules.application.domain.networking.EndpointModule.mySe‌​rverEndpoint()

Meaning you can't just extend a "mock module" and replace your original module. Nope, it's not that easy. And considering you design your components in such a way that it directly binds the Modules by class, you can't really just make a "TestComponent" either, because that'd mean you have to reinvent everything from scratch, and you'd have to make a component for every variation! Clearly that is not an option.

So on the smaller scale, what I ended up doing is making a "provider" that I give to the module, which determines whether I select the mock or the production type.

public interface EndpointProvider {
    Endpoint serverEndpoint();
}

public class ProdEndpointProvider implements EndpointProvider {

    @Override
    public Endpoint serverEndpoint() {
        return new ServerEndpoint();
    }
}


public class TestEndpointProvider implements EndpointProvider {
    @Override
    public Endpoint serverEndpoint() {
        return new TestServerEndpoint();
    }
}

@Module
public class EndpointModule {
    private Endpoint serverEndpoint;

    private EndpointProvider endpointProvider;

    public EndpointModule(EndpointProvider endpointProvider) {
        this.endpointProvider = endpointProvider;
    }

    @Named("server")
    @Provides
    public Endpoint serverEndpoint() {
        return endpointProvider.serverEndpoint();
    }
}

EDIT: Apparently as the error message says, you CAN'T override another method using a @Provides annotated method, but that doesn't mean you can't override an @Provides annotated method :(

All that magic was for naught! You can just extend a Module without putting @Provides on the method and it works... Refer to @vaughandroid 's answer.