Yeah, I like to think there are more marble tests out there in private repos. The number of downloads that rxjs-marbles receives suggests that there should be.

Hopefully, marble testing will be become more prevalent now that it’s officially supported/documented via the changes that Jay Phelps has made to the TestScheduler.

In previous versions of RxJS, the helpers — like the hold and cold observable creators — were for internal use only. rxj-marbles makes similar helpers available via a context — to avoid globals and test framework specifics. However, with the v6 changes, rxjs-marbles is now just a thin wrapper around TestScheduler#run.