TestScheduler 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。

• 即使我将 subscribeOn() 从 Schedulers.newThread() 更改为 TestScheduler() 仍然测试失败。我很困惑。我不知道是什么 我在这里做错了吗？
• 如果我删除subscribeOn,observeOn 方法然后测试成功。然后 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())
    }
}

用上面的被测类跟随测试类

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，您的测试是在一个线程上运行的，而不是您使用subscribeOn() 和observeOn() 指定的线程。无论subscribeOn()/observeOn() 中指定了什么，您想要的是让测试和被测代码在同一个线程上同步运行。

您可以使用自定义 @Rule 来实现这一点，例如 this one：

/**
 * 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都在 trampoline() 调度程序上运行。

现在只需将以下@Rule 添加到您的测试中：

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