Can you please add a test so we don't regress in the future?

sure!

lmk if there's something else I can put instead of . for the test

I think . is fine.

If you want to specify a concrete directory name, you can use something like:

let (at, mut ucmd) = at_and_ucmd!();
at.mkdir("dirname");

And then use ucmd instead of new_ucmd!.

Alright, That seems to work. Thanks for the help!!

Thanks for your PR :)