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

Can you guys check out my solution, I have included subcomponent example: https://github.com/nongdenchet/android-mvvm-with-tests. Thank you @vaughandroid, I have borrowed your overriding methods. Here is the main point:

1. I create a class to create subcomponent. My custom application will also hold an instance of this class:

   // The builder class
   public class ComponentBuilder {
    private AppComponent appComponent;
   
    public ComponentBuilder(AppComponent appComponent) {
     this.appComponent = appComponent;
    }
   
    public PlacesComponent placesComponent() {
     return appComponent.plus(new PlacesModule());
    }
   
    public PurchaseComponent purchaseComponent() {
     return appComponent.plus(new PurchaseModule());
    }
   }
   
   // My custom application class
   public class MyApplication extends Application {
   
    protected AppComponent mAppComponent;
    protected ComponentBuilder mComponentBuilder;
   
    @Override
    public void onCreate() {
     super.onCreate();
   
     // Create app component
     mAppComponent = DaggerAppComponent.builder()
             .appModule(new AppModule())
             .build();
   
     // Create component builder
     mComponentBuilder = new ComponentBuilder(mAppComponent);
    }
   
    public AppComponent component() {
     return mAppComponent;
    }
   
    public ComponentBuilder builder() {
     return mComponentBuilder;
    } 
   }
   
   // Sample using builder class:
   public class PurchaseActivity extends BaseActivity {
    ...    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
     ...
     // Setup dependency
     ((MyApplication) getApplication())
             .builder()
             .purchaseComponent()
             .inject(this);
     ...
    }
   }
   

2. I have a custom TestApplication that extends the MyApplication class above. This class contains two methods to replace the root component and the builder:

   public class TestApplication extends MyApplication {
    public void setComponent(AppComponent appComponent) {
     this.mAppComponent = appComponent;
    }
   
    public void setComponentBuilder(ComponentBuilder componentBuilder) {
     this.mComponentBuilder = componentBuilder;
    }
   }    
   

3. Finally I will try to mock or stub the dependency of module and builder to provide fake dependency to the activity:

   @MediumTest
   @RunWith(AndroidJUnit4.class)
   public class PurchaseActivityTest {
   
    @Rule
    public ActivityTestRule activityTestRule =
        new ActivityTestRule<>(PurchaseActivity.class, true, false);
   
    @Before
    public void setUp() throws Exception {
    PurchaseModule stubModule = new PurchaseModule() {
        @Provides
        @ViewScope
        public IPurchaseViewModel providePurchaseViewModel(IPurchaseApi purchaseApi) {
            return new StubPurchaseViewModel();
        }
    };
   
    // Setup test component
    AppComponent component = ApplicationUtils.application().component();
    ApplicationUtils.application().setComponentBuilder(new ComponentBuilder(component) {
        @Override
        public PurchaseComponent purchaseComponent() {
            return component.plus(stubModule);
        }
    });
   
    // Run the activity
    activityTestRule.launchActivity(new Intent());
   }