java - Mocking an injected field in unit tests -

i have presenter class uses field injected through dagger, looks this:

public class rsslistpresenter {      @inject     rssservice rssservice; // <-- injected field      public rsslistpresenter() {         setupdi();     }      private void setupdi() {         daggernetworkcomponent.builder()                 .networkmodule(new networkmodule())                 .build()                 .inject(this);     }      public void loaditems() {         rss rss = rssservice.getrssfeed()         // ....     } } 

everything works fine. now, unit test rsslistpresenter class. question how provide mock rssservice presenter?

ofcourse can add new method setrssservice(rssservice rssservice) presenter , use provide mock unit tests, adding method unit tests not feel right. correct way handle this?

for completeness here module , component declarations:

@singleton @component(modules = networkmodule.class) public interface networkcomponent {     void inject(rsslistpresenter presenter); }  @module public class networkmodule {      @provides     retrofit provideretrofit() {         // ...      }      @provides     @singleton     rssservice providepcworldrssservice(retrofit retrofit) {         return retrofit.create(rssservice.class);     }  } 

property injection not easy test. in case, constructor injection better. refactor constructor this:

private final rssservice rssservice;  @inject public rsslistpresenter(rssservice rssservice) {         this.rssservice = rssservice; } 

now can test easily:

//mocks rssservice mockrssservice;  //system under test rsslistpresenter rsslistpresenter;  @before public void setup() {     mockrssservice = mockito.mock(rssservice.class);     rsslistpresenter = new rsslistpresenter(mockrssservice); } 

you shouldn't using daggernetworkcomponent.inject(this) inside rsslistpresenter. instead should configuring dagger when injects members top-level classes (activity, fragment, service) can access object graph , create instance of rsspresenter.

why put injectors in activity , service , not in rsslistpresenter? these classes instantiated android system , have no choice use injectors.

to clarify, activity, fragment etc. ideal injection targets. rsslistpresenter etc. injected dependencies. need configure dependency injection framework, dagger, can provide correct dependencies inject injection targets.

so need write @provides method rsslistpresenter

@provides providersslistpresenter(rssservice rssservice) {     return new rsslistpresenter(rssservice); }