This chapter has taken us deep into RxJS by covering topics such as hot, cold, and warm Observables, and what that generally means in terms of when to subscribe to a stream and how they share their Producer under certain conditions. Next up, we covered Subjects, and the fact that Observable isn't the only thing you can subscribe to. Subjects also allow as to append values to the stream whenever we want, and we also learned that there exist different types of Subjects, depending on the situation at hand.

We ventured deeper into an important topic, testing, and tried to explain the difficulty in testing asynchronous code. We talked about the current state of the testing situation and what libraries to use here and now for your testing scenarios. Lastly, we covered pipeable operators, and our new preferred way of importing and composing operators to ensure we end up with the smallest possible bundle size. 

With all this RxJS knowledge, it is now time to take on the Redux pattern and its core concepts in the coming chapter, so we are ready to tackle NgRx in the final chapter of this book. It's time to get excited, if you weren't before.