如何使用Mockito在单元测试中模拟ObservableTransformer

Question

为了获得可重用和可测试的rxjava代码，我使用ObservableTransformers分离了代码的各个部分。它在生产中工作得很好，但是测试它并不像预期的那么容易，因为我似乎无法模拟那些观察到的ransformers。

import io.reactivex.Observable;
import io.reactivex.ObservableTransformer;
import io.reactivex.subjects.PublishSubject;

public class Cut {

    private PublishSubject<String> emitter = PublishSubject.create();
    private ITransformerProvider transformerProvider;

    public Cut(ITransformerProvider transformerProvider) {
        this.transformerProvider = transformerProvider;
    }

    public void writeNewText(String text){
        emitter.onNext(text);
    }

    public Observable<String> getActualText(){
        return emitter
                .compose(transformerProvider.getObservableTransformer());
    }

    class MyActualObservableTransformer implements ITransformerProvider {
        @Override
        public ObservableTransformer<String, String> getObservableTransformer() {
            //does something I do not want to execute in unit test, e.g. REST call
            return null;
        }
    }
}

import io.reactivex.ObservableTransformer;

public interface ITransformerProvider {
    ObservableTransformer<String, String> getObservableTransformer();
}

public class TextTest {

    @Mock
    private ITransformerProvider transformerProvider;
    @Mock
    private ObservableTransformer<String, String> observableTransformer;

    private TestObserver<String> testObserver;
    private Cut cut;


    @Before
    public void setup(){
        MockitoAnnotations.initMocks(this);

        when(transformerProvider.getObservableTransformer()).thenReturn(observableTransformer);
        when(observableTransformer.apply(any())).thenReturn(Observable.just("mockedText"));

        testObserver = new TestObserver<>();
        cut = new Cut(transformerProvider);

        cut.getActualText()
            .observeOn(Schedulers.trampoline())
            .subscribe(
                    newText -> testObserver.onNext(newText)
                    , error -> Assert.fail(error.getMessage()));
    }

    @Test
    public void testGetActualText(){
        cut.writeNewText("ignoredText");
        testObserver.assertValueAt(0, text -> text.equals("mockedText"));
    }
}

when（observableTransformer.apply（any（）））.thenreturn（observable.just（“mockedtext”））；

一旦调用subscribe for它，它就会发出一个新值，订阅链永远不会完成。所以我的问题是，我如何模拟一个可观察的，而不让它在订阅期间发出值？我想Observable.just或BehaviorSubject并不适合，因为就我仍然有限的RxJava知识而言，它在本例中的行为与预期一致。有什么想法吗？

Answer 1

我想出的最简单的解决方案就是不要用Mockito来嘲笑它，而是自己去嘲笑它：

private ObservableTransformer ObservableTransformer=text->text.map（忽略->“mockedtext”）；