While `nix develop` should work perfectly fine for development, contributors may prefer to enable [`direnv`](https://direnv.net/) or [`nix-direnv`](https://github.com/nix-community/nix-direnv) support.
From the project folder:
```bash
direnv allow
```
If using an editor, it may be preferable to adopt an addon to enter the environment:
If you're hacking on `nix-installer`, you likely already have Nix and cannot test locally.
> That's probably a good thing! You should test in a sandbox.
Automated [`qemu` tests][#qemu-vm-tests] exist and should be preferred for oneshot testing of changes.
For interactive testing, tools like [`libvirt`](https://libvirt.org/) via [`virt-manager`](https://virt-manager.org/) or [`vagrant`](https://www.vagrantup.com/) can be used to spin up machines and run experiments.
When running such interactive tests, consider creating a snapshot of the VM right before running the installer, so you can quickly roll back if something happens.
In general, it's a good idea to test on the closest you can get to the desired target environment. For example, when testing the Steam Deck planner it's a good idea to run that test in a Steam Deck VM as described in detail in the planner.
<details>
<summary><strong>Adding a planner for specific hardware?</strong></summary>
Please include an full guide on how to create the best known virtual testing environment for that device.
**A link is not sufficient, it may break.** Please provide a full summary of steps to take, link to any original source and give them credit if it is appropriate.
It's perfectly fine if they are manual or labor intensive, as these should be a one time thing and get snapshotted prior to running tests.
</details>
## `qemu` VM tests
In `nix/tests/vm-test` there exists some Nix derivations which we expose in the flake via `hydraJobs`.
These should be visible in `nix flake show`:
```
❯ nix flake show
warning: Git tree '/home/ana/git/determinatesystems/nix-installer' is dirty
<summary><strong>Adding a distro?</strong></summary>
Notice how `rhel-v7` has a `v7`, not just `7`? That's so the test output shows correctly, as Nix will interpret the first `-\d` (eg `-7`, `-123213`) as a version, and not show it in the output.
The `action.yml` is used directly in the CI process, so it is automatically tested for most changes.
If you are working on the `action.yml` There is an integration test for `action.yml` at https://github.com/DeterminateSystems/nix-installer-example. You can create PRs there to prompt rebuilds, please refer to what you might be working on in the PR description so readers can easily find your work. (The commits don't have to be meaningful, `git commit --allow-empty -m "prod at ci"` is perfectly reasonable.)
