Some utils' behavior may change depending on the stdout().is_terminal() answer.
This is the case for ls which adapts its default quoting style depending on STDOUT being a TTY or not.

The issue is that from what I saw, the testing utilities do not provide any way to test these TTY behaviors.

Maybe we could adapt the utilities to offer such verifications.
A straighforward way to go would be to use the pty_process crate.