Dagger 2单元测试中的现场注入

Question

class ThingDoer {
  private final ThingGetter getter;
  private final ThingPutter putter;

  @Inject ThingDoer(ThingGetter getter, ThingPutter putter) {
    this.getter = getter;
    this.putter = putter;
  }

  String doTheThing(int howManyTimes) { /* … */ }
}

class ThingDoer {
    @Inject
    ThingGetter getter;

    @Inject
    ThingPutter putter;

    @Inject
    ThingMaker maker;

    @Inject
    // other 10 objects

    public ThingDoer() {
        App.getThingComponent().inject(this);
    }

    String doTheThing(int howManyTimes) { /* … */ }
}

正如您所看到的，我不再使用构造函数注入，而是使用字段注入。主要原因是构造函数中没有太多的参数。

当ThingDoer的所有依赖项都使用字段注入提供时，是否有方法在其中注入模拟依赖项？

Answer 1

对于字段注入，您可以创建一个组件和一个模块，它们在单元测试中使用。

假设您有单元测试类ThingDoerTest，您可以使组件将依赖项注入到ThingDoerTest而不是ThingDoer，并且模块提供模拟对象而不是真实对象。

在我的项目中，HomeActivity有一个字段注入HomePresenter。下面的代码是一些片段。希望代码能给你一些想法。

@RunWith(AndroidJUnit4.class)
public class HomeActivityTest implements ActivityLifecycleInjector<HomeActivity>{

    @Rule
    public InjectorActivityTestRule<HomeActivity> activityTestRule = new InjectorActivityTestRule<>(HomeActivity.class, this);

    @Inject
    public HomePresenter mockHomePresenter;

    @Override
    public void beforeOnCreate(HomeActivity homeActivity) {
        Instrumentation instrumentation = InstrumentationRegistry.getInstrumentation();
        MyApplication myApplication = (MyApplication) instrumentation.getTargetContext().getApplicationContext();

        TestHomeComponent testHomeComponent = DaggerHomeActivityTest_TestHomeComponent.builder()
            .appComponent(myApplication.getAppComponent())
            .mockHomeModule(new MockHomeModule())
            .build();
        testHomeComponent.inject(HomeActivityTest.this);
        homeActivity.setHomeComponent(testHomeComponent);
    }

    @Test
    public void testOnCreate() throws Exception {
        verify(mockHomePresenter).start();
    }

    @ActivityScope
    @Component(
        dependencies = {
            AppComponent.class
        },
        modules = {
            MockHomeModule.class
        }
    )
    public interface TestHomeComponent extends HomeComponent {
        void inject(HomeActivityTest homeActivityTest);
    }

    @Module
    public class MockHomeModule {
        @ActivityScope
        @Provides
        public HomePresenter provideHomePresenter() {
            return mock(HomePresenter.class);
        }
    }

}