examplenetwork.java

public interface DemoService {
    @GET("/somesuffix")
    void getData(Callback<List<Data>> callback);
}


public class MockDemoService implements DemoService {
  public void getData(Callback<List<Data>> callback){
    //do your own implementation for mocking
    throw new IllegalStateException("Stub");
  }
}

public class NetworkModule {
  
  @Provides
    @Singleton
    DemoService providesDemoService(@Named("okclient") OkClient okClient) {
        return new RestAdapter.Builder()
                .setClient(okClient)
                .setEndpoint("https://www.yourdomain.com")
                .build()
                .create(DemoService.class);
    }
}

//Simply provide this module to your dagger builder instead of actual module
public class MockNetworkModule extends NetworkModule {

    @Override
    DemoService providesDemoService(@Named("okclient") OkClient okClient) {
        return new MockDemoService();
    }
}