如何测试RxJava和改造

1.摆脱静态调用-使用依赖注入

代码中的第一个问题是您使用静态方法.这不是一个可测试的体系结构，至少不容易，因为它使模拟实现变得更加困难. 为了正确执行操作，而不是使用访问ApiClient.getService()的Api，而是通过构造函数向演示者注入此服务:

How to test RxJava and Retrofit

1. Get rid of the static call - use dependency injection

The first problem in your code is that you use static methods. This is not a testable architecture, at least not easily, because it makes it harder to mock the implementation. To do things properly, instead of using Api that accesses ApiClient.getService(), inject this service to the presenter through the constructor:

public class SplashPresenterImpl implements SplashPresenter {

private SplashView splashView;
private final ApiService service;

public SplashPresenterImpl(SplashView splashView, ApiService service) {
    this.splashView = splashView;
    this.apiService = service;
}

2.创建测试课程

在@Before方法中实现JUnit测试类并使用模拟依赖项初始化演示者:

2. Create the test class

Implement your JUnit test class and initialize the presenter with mock dependencies in the @Before method:

public class SplashPresenterImplTest {

@Mock
ApiService apiService;

@Mock
SplashView splashView;

private SplashPresenter splashPresenter;

@Before
public void setUp() throws Exception {
    this.splashPresenter = new SplashPresenter(splashView, apiService);
}

3.模拟并测试

然后是实际的模拟和测试，例如:

3. Mock and test

Then comes the actual mocking and testing, for example:

@Test
public void testEmptyListResponse() throws Exception {
    // given
    when(apiService.syncGenres()).thenReturn(Observable.just(Collections.emptyList());
    // when
    splashPresenter.syncGenres();
    // then
    verify(... // for example:, verify call to splashView.navigateToHome()
}

这样，您可以测试Observable +订阅，如果要测试Observable的行为是否正确，请使用TestSubscriber实例进行订阅.

That way you can test your Observable + Subscription, if you want to test if the Observable behaves correctly, subscribe to it with an instance of TestSubscriber.

在使用RxJava和RxAndroid调度程序(例如Schedulers.io()和AndroidSchedulers.mainThread())进行测试时，在运行可观察/订阅测试时可能会遇到一些问题.

When testing with RxJava and RxAndroid schedulers, such as Schedulers.io() and AndroidSchedulers.mainThread() you might encounter several problems with running your observable/subscription tests.

第一个是在应用给定调度程序的行上抛出的NullPointerException，例如:

The first is NullPointerException thrown on the line that applies given scheduler, for example:

.observeOn(AndroidSchedulers.mainThread()) // throws NPE

原因是AndroidSchedulers.mainThread()在内部是使用Android的Looper线程的LooperScheduler.此依赖关系在JUnit测试环境中不可用，因此调用会导致NullPointerException.

The cause is that AndroidSchedulers.mainThread() is internally a LooperScheduler that uses android's Looper thread. This dependency is not available on JUnit test environment, and thus the call results in a NullPointerException.

第二个问题是，如果应用的调度程序使用单独的工作线程执行可观察的任务，则竞争条件发生在执行@Test方法的线程与所述工作线程之间.通常，它会导致测试方法在可观察到的执行完成之前返回.

The second problem is that if applied scheduler uses a separate worker thread to execute observable, the race condition occurs between the thread that executes the @Test method and the said worker thread. Usually it results in test method returning before observable execution finishes.

通过提供符合测试要求的调度程序，可以轻松解决上述两个问题，并且选择很少:

Both of the said problems can be easily solved by supplying test-compliant schedulers, and there are few options:

1. 使用RxJavaHooks和RxAndroidPlugins API覆盖对Schedulers.?和AndroidSchedulers.?的任何调用，从而强制使用Observable，例如Scheduler.immediate():

1. Use RxJavaHooks and RxAndroidPlugins API to override any call to Schedulers.? and AndroidSchedulers.?, forcing the Observable to use, for example, Scheduler.immediate():

@Before
public void setUp() throws Exception {
        // Override RxJava schedulers
        RxJavaHooks.setOnIOScheduler(new Func1<Scheduler, Scheduler>() {
            @Override
            public Scheduler call(Scheduler scheduler) {
                return Schedulers.immediate();
            }
        });

        RxJavaHooks.setOnComputationScheduler(new Func1<Scheduler, Scheduler>() {
            @Override
            public Scheduler call(Scheduler scheduler) {
                return Schedulers.immediate();
            }
        });

        RxJavaHooks.setOnNewThreadScheduler(new Func1<Scheduler, Scheduler>() {
            @Override
            public Scheduler call(Scheduler scheduler) {
                return Schedulers.immediate();
            }
        });

        // Override RxAndroid schedulers
        final RxAndroidPlugins rxAndroidPlugins = RxAndroidPlugins.getInstance();
        rxAndroidPlugins.registerSchedulersHook(new RxAndroidSchedulersHook() {
            @Override
            public Scheduler getMainThreadScheduler() {
                return Schedulers.immediate();
        }
    });
}

@After
public void tearDown() throws Exception {
    RxJavaHooks.reset();
    RxAndroidPlugins.getInstance().reset();
}

此代码必须包装Observable测试，因此可以如图所示在@Before和@After中完成，可以将其放入JUnit @Rule中或放置在代码中的任何位置.只是不要忘记重置钩子.

This code has to wrap the Observable test, so it can be done within @Before and @After as shown, it can be put into JUnit @Rule or placed anywhere in the code. Just don't forget to reset the hooks.

第二个选项是通过依赖注入为类(Presenters，DAO)提供显式的Scheduler实例，然后再次使用Schedulers.immediate()(或其他适合测试的对象).

Second option is to provide explicit Scheduler instances to classes (Presenters, DAOs) through dependency injection, and again just use Schedulers.immediate() (or other suitable for testing).

如@aleien所指出的，您还可以使用执行Scheduler应用程序的注入的RxTransformer实例.

As pointed out by @aleien, you can also use an injected RxTransformer instance that executes Scheduler application.

我在生产中使用了第一种方法，效果很好.

I've used the first method with good results in production.