如何在Android中使用Dagger2 Dependency Injection和Robolectric进行测试？

Question

我最近将Dagger2应用到Android应用程序中以便于依赖注入,但在这样做后,我的一些测试已停止工作.

现在我想了解如何调整我的测试以使用Dagger2？我正在使用Robolectric来运行我的测试.

以下是我如何使用Dagger2,我最近才学会它,所以这可能是不好的做法,并没有帮助测试,所以请指出我可以做的任何改进.

我有一个AppModule,如下所示:

@Module
public class MyAppModule {

    //Application reference
    Application mApplication;

    //Set the application value
    public MyAppModule(Application application) {
        mApplication = application;
    }

    //Provide a singleton for injection
    @Provides
    @Singleton
    Application providesApplication() {
        return mApplication;
    }
}

我称之为NetworkModule,提供注入对象,如下所示:

@Module
public class NetworkModule {

private Context mContext;

//Constructor that takes in the required context and shared preferences objects
public NetworkModule(Context context){
    mContext = context;
}

@Provides
@Singleton
SharedPreferences provideSharedPreferences(){
    //...
}

@Provides @Singleton
OkHttpClient provideOKHttpClient(){
    //...
}

@Provides @Singleton
Picasso providePicasso(){
    //...
}

@Provides @Singleton
Gson provideGson(){
    //...
}
}

然后组件是这样的:

Singleton
@Component(modules={MyAppModule.class, NetworkModule.class})
public interface NetworkComponent {

    //Activities that the providers can be injected into
    void inject(MainActivity activity);
    //...
}

对于我的测试,我使用的是Robolectric,我的Application类的Test变量如下:

public class TestMyApplication extends TestApplication {

    private static TestMyApplication sInstance;
    private NetworkComponent mNetworkComponent;

    @Override
    public void onCreate() {
        super.onCreate();
        sInstance = this;
        mNetworkComponent = DaggerTestMyApplication_TestNetworkComponent.builder()
                .testMyAppModule(new TestMyAppModule(this))
                .testNetworkModule(new TestNetworkModule(this)).build();
    }

    public static MyApplication getInstance() {
        return sInstance;
    }

    @Override public NetworkComponent getNetComponent() {
        return mNetworkComponent;
    }
}

正如您所看到的,我正在尝试确保使用我的Dagger2模块的模拟版本,这些也被模拟,模拟的MyAppModule返回TestMyApplication和模拟的NetworkModule返回模拟对象,我还有一个模拟的NetworkComponent,它扩展了真实NetworkComponent.

在测试的设置中,我使用Robolectric创建Activity,如下所示:

//Build activity using Robolectric
ActivityController<MainActivity> controller = Robolectric.buildActivity(MainActivity.class);
activity = controller.get();

controller.create(); //Create out Activity

这会创建Activity并启动onCreate,这就是问题发生的地方,在onCreate中我有以下代码片段将Activity注入组件,因此它可以像这样使用Dagger2:

@Inject Picasso picasso; //Injected at top of Activity

super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
MyApplication.getInstance().getNetComponent().inject(this); 

picasso.load(url).fetch();

这里的问题是,当运行测试时,我在picasso变量上得到一个NullPointerException,所以我猜我的Dagger2设置在测试的某个地方有一个缺失的链接？

编辑:添加TestNetworkModule

@Module
public class TestNetworkModule {

    public TestNetworkModule(Context context){

    }

    @Provides
    @Singleton
    SharedPreferences provideSharedPreferences(){
        return Mockito.mock(SharedPreferences.class);
    }


    @Provides @Singleton
    Gson provideGson(){
        return Mockito.mock(Gson.class);
    }

    @Provides @Singleton
    OkHttpClient provideOKHttpClient(){
        return Mockito.mock(OkHttpClient.class);
    }

    @Provides @Singleton
    Picasso providePicasso(){
        return  Mockito.mock(Picasso.class);
    }

}

Answer 1

您无需在TestApplication和模块中添加setter.您正在使用Dagger 2,因此您应该使用它来在测试中注入依赖项:

首先在MyApplication中创建一个检索ApplicationComponent的方法.此方法将在TestMyApplication类中重写:

public class MyApplication extends Application {

    private ApplicationComponent mApplicationComponent;

    public ApplicationComponent getOrCreateApplicationComponent() {
        if (mApplicationComponent == null) {
            mApplicationComponent = DaggerApplicationComponent.builder()
                    .myAppModule(new MyAppModule(this))
                    .networkModule(new NetworkModule())
                    .build();
        }
        return mApplicationComponent;
    }
}

然后创建一个TestNetworkComponent:

@Singleton
@Component(modules = {MyAppModule.class, TestNetworkModule.class})
public interface TestApplicationComponent extends ApplicationComponent {
    void inject(MainActivityTest mainActivityTest);
}

在TestNetworkModule中返回一个mock

@Provides
@Singleton
Picasso providePicasso(){
    return Mockito.mock(Picasso.class);
}

在TestMyApplication中,构建TestNetworkComponent:

public class TestMyApplication extends MyApplication {

    private TestApplicationComponent testApplicationComponent;

    @Override
    public TestApplicationComponent getOrCreateApplicationComponent() {
        if (testApplicationComponent == null) {
            testApplicationComponent = DaggerTestApplicationComponent
                    .builder()
                    .myAppModule(new MyAppModule(this))
                    .testNetworkModule(new TestNetworkModule())
                    .build();
        }
        return testApplicationComponent;
    }
}

然后在MainActivityTest中运行应用程序标记并注入依赖项:

@RunWith(RobolectricGradleTestRunner.class)
@Config(constants = BuildConfig.class, sdk = 21, application = TestMyApplication.class)
public class MainActivityTest {

    @Inject
    Picasso picasso;

    @Before
    public void setup() {
        ((TestMyApplication)RuntimeEnvironment.application).getOrCreateApplicationComponent().inject(this);
        Mockito.when(picasso.load(Matchers.anyString())).thenReturn(Mockito.mock(RequestCreator.class));
    }


    @Test
    public void test() {
        Robolectric.buildActivity(MainActivity.class).create();
    }

}

你的Picasso领域已经注入你的Picasso模拟现在你可以与之互动.