Introducing TestObserver and TestSubscriber

As you read through this chapter, you may have developed an idea that the only way we can perform tests are through blocking the code, either by using blockingSubscribe or by using blocking operators. But this is not the case. In fact, there are more comprehensive ways to reactive code, or rather we can say that we can test reactive code reactively.

To say it more precisely, in a Subscriber we have onError and onComplete that demands testing along with onNext, which is not always possible with just blocking. Yes some sort of blocking is necessary, but it cannot alone do all the things and it also needs to be managed reactively.

So, here are your two superheroes to make the developers life easy—TestObserver and TestSubscriber. As with Subscriber and Observer, you can use TestSubscriber with Flowables and TestObserver with Observables, everything except that is similar between these two.

So, let's get started with an example:

    @Test 
    fun `test...