Using `docker compose` in addition to `docker` for convenient mounting of `n` script and the tests into the container. Changes to the tests or to `n` itself are reflected immediately without needing to rebuild the containers.
`bats` is being mounted directly out of `node_modules` into the container as a manual install based on its own install script. This is a bit of a hack, but avoids needing to install `git` or `npm` for a full remote install of `bats`, and means everything on the same version of `bats`.