That's a good point, and one that I've forgotten since I've been out of the JS world for a while now! Often you're trying to run the code in different environments depending on the context, which does require a lot of extra build tool support. Consolidating that is a reasonable goal, I'd say.
It will be neat to see where they draw the line. For example, will Rome include an assertion library? What about mock and fake support? That feels a bit far from what Rome is trying to do, but if they've implemented a test runner, maybe defaults provided would be good for the DX?
_That_ is an excellent question, and I honestly have no idea what their plans are in that respect :) I've seen a number of Sebastian's tweets over the last couple years as he was working on Rome, and have glanced at the repo README, but haven't poked at the actual work they're doing.
Part of the sales pitch for Jest is that it includes a set of APIs for mocking and assertions built in. Wouldn't surprise me if Rome did the same, but curious how they'd design things.
It will probably include module-mocking in it (aka jest.mock), since it happens during "bundling"/compilation, but the assertion and function mocking can certainly be handled by a third-party library.
It will be neat to see where they draw the line. For example, will Rome include an assertion library? What about mock and fake support? That feels a bit far from what Rome is trying to do, but if they've implemented a test runner, maybe defaults provided would be good for the DX?