Switch to jest for unit testing?

[lgeiger]

Atom's test runner uses Jasmine 1.3 which was released in 2012. Unfortunately they can't upgrade this easily since they would break all community packages.

With nteract slowly switching to jest, I think we should evaluate if switching to jest makes sense for Hydrogen too. I recently saw that prettier-atom also uses jest for testing despite beeing a Atom package. That's what got me thinking about using it as well.

Here are what I think are the Pros and Cons of jest for our use case:

Pros	Cons
far superior mocking capabilities	we would lose access to the atom global and can't use require('atom') (unless one writes a Atom test runner, which seams a bit flaky) so we definitely need those mocking capabilities
better support for async tests	more dependencies and initial setup, e.g. we need to set up babel for transpiling the tests
more features like snapshots, coverage, test watching, ...	devs need Node and npm installed
new and shiny (very subjective, only "real" benefit: devs may end up writing more tests)	no graphical UI for beginners

prettier-atom also has a custom babel transpile step, but I don't really see the benefit compared to our current setup, especially since we would need to check in the generated files due to apms packaging system (atom/apm#498)

Just putting this out there since jest seams pretty cool but I haven't used it much so I wonder if we would benefit from it despite loosing access to Atom's API.

What do you think?

[BenRussert]

Do you know of any other Atom packages using jest? Either way I was thinking it might be good to see if we could get a discussion started on the atom forums.

Maybe others have tried or have some input on the pros and cons. If we would be "pioneering" this there might be some good feedback on challenges we might face.