Test2 is a Perl distribution that replaces a bunch of older test stuff. See https://metacpan.org/pod/Test2

But unlike TAP, it's fairly Perl-specific as opposed to just being an output format. I imagine you could adapt the ideas in it to Node but it'd be more complex than simply implement TAP in JS.

And yes, I think the idea of having different output formats makes sense. With Test2, the test _harness_ produces TAP from the underlying machine-readable format, rather than having the test code itself directly product TAP. The harness is a separate program that executes the tests.