V2 test runner

[quintuple-mallard]

In a bit, after I've implemented some exercises and more tooling for Nushell, I'll work on getting the track to a V2 test runner.
I'm thinking of using something with scope commands similar to Testing your Nushell code in the Nushell docs, but since source is a parser keyword, a simple implementation with a generic test file something like this won't work.

So my question is, is it better to have a generic file with a placeholder that will be substituted by sed or something similar, or to provide a file to run tests with each exercise?

[quintuple-mallard]

I think sed is probably too error-prone when I think about it