[turboponyy]

Yes. GitHub actions can be just a thin wrapper to call any Nix commands that you can run locally.

> How do you automate running tests

You just build the Nix derivation that runs your tests, e.g. `nix build #tests` or `nix flake check` in your workflow file.

> deploying to dev on every push

You can set up a Nix `devShell` as a staging area for any operations you'd need to perform for a deployment. You can use the same devShell both locally and in CI. You'd have to inject any required secrets into the Action environment in your repository settings, still. It doesn't matter what your staging environment is comprised of, Nix can handle it.