# Developing

Three tools, from instant to slow. Run them from the repository root; the
flake only sees files git knows about, so `git add` new files first.

## `nix run .#webui-dev`: the web UI on your machine

Sample settings, sample DHCP leases and your real interface counters, on
<https://127.0.0.1:8443> (password `devpassword1`). Templates and CSS are
re-read on every request: edit, reload the browser. A template with a typo
keeps the last good version and logs the error. Pings need root and show "no
answer"; Apply does nothing useful here.

## `nix run .#fast`: no VMs

Go formatting, vet and tests, then builds the installer, a router built from
settings (through the release) and the home gateway. That runs shellcheck over
the scripts and evaluates the modules: most failures of the VM tests
(typos, type errors, a script that does not build) show up here, in about a
minute (half of that when little changed).

    nix run .#fast -- --drivers   also builds every VM test's driver: type-checks
                                  the test scripts, builds the VMs' systems
    nix run .#fast -- --all       also the checks that need no VM and `nix flake check`

## `nix run .#test -- NAME...`: VM tests

One at a time (each needs gigabytes of memory), a line per test with its time,
and for a failure the step that failed and what it said; the full log is in
`${TMPDIR:-/tmp}/router-test-logs/NAME.log`.

    nix run .#test -- update setup
    nix run .#test -- --all
    nix run .#test -- --list

`nix run .#test -- -i update` builds the test's interactive driver and gives a
Python prompt: `start_all()`, `target.succeed("...")`, `test_script()`. Boot
the VMs once and try a step again instead of running the whole test.

### Where the time goes

A VM test spends most of its time in the system under test, not in building:
`router-install` (about a minute), booting (20 s each), and everything that
runs `router-apply` on the router (building a NixOS system there takes about a
minute) or waits for a rollback timer. A source change rebuilds the systems
again on the host. So:

Measured (one at a time): `webui` 45 s, `ddns` 43 s, `basic` 107 s, `onestick` 77 s; the
ones that install and rebuild on the device are the slow ones: `apply` and
`update` several minutes, `setup` 11 minutes (three installs).

- Try a change with `webui-dev` or `fast` first; run a VM test only to confirm.
- A change to the web UI only needs `webui` (a single node, no install).
  `apply`, `setup` and `update` are for what an installed router does:
  on-device builds, rollback, `router-setup`, `router-update`. Run them
  before a release or when you touched those, not after every UI edit.
- Nix does not rerun a test whose inputs did not change, so `--all` after a
  small change is cheaper than it looks, except that the web UI is part of
  every installed system: any change to it invalidates `apply`, `setup`
  and `update`.
- Use `-i` to iterate on a test script.