测试调度程序在测试特定用例时不起作用

Question

我正在测试单个用例。 但是测试观察者不会在测试环境中发出任何东西。

• 即使我subscribeOn()从Schedulers.newThread()更改为 TestScheduler()测试仍然失败。我很困惑。我不知道是什么我在这里做错了？
• 如果我删除subscribeOn，observeOn方法，则测试通过成功。TestScheduler()的实际用途是什么？

以下是UseCase.kt文件

abstract class UseCase<T>(val postExecutionThread: PostExecutionThread) {
    abstract fun buildUseCaseBuilder(): Observable<T>
    /**
     * execute method for observables
     */
    open fun execute(): Observable<T> {
        return buildUseCaseBuilder()
                .subscribeOn(Schedulers.newThread())
                .observeOn(postExecutionThread.getScheduler())
    }
}

遵循测试类

与上述被测试类

class UseCaseTest {
    val postExecutionThread=Mockito.mock(PostExecutionThread::class.java)
    val result: String="test"
    val testObserver=TestObserver<String>()
    @Before
    fun setUp() {
        _when(postExecutionThread.getScheduler()).thenReturn(TestScheduler())
    }
    @Test
    fun `test execute method of use case`() {
        println(" thread type ${postExecutionThread.getScheduler()}")
        //test fail
        //java.lang.AssertionError: Value count differs; Expected: 1 [test], Actual: 0 [] (latch = 1, values = 0, errors = 0, completions = 0)
        TestUseCase(postExecutionThread).execute().test()
                .assertResult(result)
        //subscriber not print any thing
        TestUseCase(postExecutionThread).execute().subscribe{
            println("called $it")
        }
    }
    inner class TestUseCase(postExecutionThread: PostExecutionThread?) : UseCase<String>(postExecutionThread!!) {
        override fun buildUseCaseBuilder(): Observable<String> {
            return Observable.just(result)
        }
    }
}

Answer 1

问题是，您的测试是在您使用 subscribeOn() 和 observeOn() 指定的线程以外的线程上运行的。您想要的是使测试和测试的代码在同一线程上同步运行，而不管在 subscribeOn()/observeOn() 中指定了什么。

您可以使用如下所示的自定义@Rule来实现这一点：

/**
 * This rule registers Handlers for RxJava and RxAndroid to ensure that subscriptions
 * always subscribeOn and observeOn Schedulers.trampoline().
 * Warning, this rule will reset RxAndroidPlugins and RxJavaPlugins before and after each test so
 * if the application code uses RxJava plugins this may affect the behaviour of the testing method.
 */
public class RxSchedulersOverrideRule implements TestRule {
    private final Function<Callable<Scheduler>, Scheduler> mRxAndroidSchedulersHook =
            new Function<Callable<Scheduler>, Scheduler>() {
                @Override
                public Scheduler apply(@NonNull Callable<Scheduler> schedulerCallable)
                        throws Exception {
                    return getScheduler();
                }
            };
    private final Function<Scheduler, Scheduler> mRxJavaImmediateScheduler =
            new Function<Scheduler, Scheduler>() {
                @Override
                public Scheduler apply(@NonNull Scheduler scheduler) throws Exception {
                    return getScheduler();
                }
            };
    @Override
    public Statement apply(final Statement base, Description description) {
        return new Statement() {
            @Override
            public void evaluate() throws Throwable {
                RxAndroidPlugins.reset();
                RxAndroidPlugins.setInitMainThreadSchedulerHandler(mRxAndroidSchedulersHook);
                RxJavaPlugins.reset();
                RxJavaPlugins.setIoSchedulerHandler(mRxJavaImmediateScheduler);
                RxJavaPlugins.setNewThreadSchedulerHandler(mRxJavaImmediateScheduler);
                base.evaluate();
                RxAndroidPlugins.reset();
                RxJavaPlugins.reset();
            }
        };
    }
    public Scheduler getScheduler() {
        return Schedulers.trampoline();
    }
}

使用此代码，您可以拦截所有调度程序，并使所有内容在调度程序上运行trampoline()。

现在只需将以下@Rule添加到测试中：

 
    public class MyTestClass {
        @Rule
        public final RxSchedulersOverrideRule mOverrideSchedulersRule = new RxSchedulersOverrideRule();
        @Test
        public void someTest() {
            ...
        }
    }