Well, you can start the “REPL-like” server that will receive the code, and then will use Code.eval_string/3 to execute whatever you throw at it. It will provide similar experience to the SLIME.
About unit testing, what I am using is entr. So you need to list all files in your project (I am using rg -l -telixir '', but you can use git ls-files instead) and then make it to output name of the changed file entr echo /_ that will pass the changed files to mix test --listen-on-stdin --stale. So whole CLI will look like:
rg -l -telixir '' | entr echo /_ | mix test --listen-on-stdin --stale
Now it will changed tests on each save.
