Once you start your path to master Observables, the chances are high that you already encountered a marble diagram on your way.
The marble syntax is a very intuitive syntax to represent streams, and it is often used to visualize observable transformations. It is not only a form of documentation, but it can also be used to test our Observables.
From consulting various developers, I have seen that teams often take advantage of a third-party library to apply marble testing. Using a third-party library is a valid approach, and there’s nothing wrong with it. But!