I am working on my first NixOS configuration and want to TDD each service as I bring it up.
I’ve put this together as a sample configuration (using this post for clues):
{
inputs.nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
outputs = { self, nixpkgs, ... }:
let
system = "x86_64-linux";
hello-world-module = { pkgs, lib, ... }:
let
hello-world-server = pkgs.runCommand "hello-world-server" { } ''
mkdir -p $out/{bin,/share/webroot}
cat > $out/share/webroot/index.html <<EOF
<html><head><title>Hello world</title></head><body><h1>Hello World!</h1></body></html>
EOF
cat > $out/bin/hello-world-server <<EOF
#!${pkgs.runtimeShell}
exec ${lib.getExe pkgs.python3} -m http.server 8000 --dir "$out/share/webroot"
EOF
chmod +x $out/bin/hello-world-server
'';
in
{
systemd.services.hello-world-server = {
after = [ "network.target" ];
wantedBy = [ "multi-user.target" ];
serviceConfig = {
DynamicUser = true;
ExecStart = lib.getExe hello-world-server;
};
};
services.getty.autologinUser = "root";
virtualisation.vmVariant.virtualisation.graphics = false;
boot.loader = {
systemd-boot.enable = true;
efi.canTouchEfiVariables = true;
};
nixpkgs.hostPlatform = system;
system.stateVersion = "23.11";
};
in
{
checks.${system} = {
check-hello-world =
let
pkgs = nixpkgs.legacyPackages.${system};
inherit (pkgs) lib;
nixos-lib = import (pkgs.path + "/nixos/lib") { };
in
# run test with `nix flake check`
(nixos-lib.runTest {
hostPkgs = pkgs;
defaults.documentation.enable = lib.mkDefault false;
node.specialArgs = { inherit self; };
name = "check-hello-world";
nodes.machine = { self, pkgs, ... }: {
imports = [ hello-world-module ];
environment.systemPackages = [ pkgs.curl ];
};
testScript = ''
start_all()
machine.wait_for_unit("hello-world-server")
machine.wait_for_open_port(8000)
output = machine.succeed("curl localhost:8000/index.html")
assert "Hello world" in output, f"'{output}' does not contain 'Hello world'"
'';
}).config.result;
};
# XXX: how can i uncomment this so build-vm works without breaking `nix flake check`???
# if I uncomment this, i can build/run the vm
#
## run vm with `nix build '.#nixosConfigurations.demo.config.system.build.vm' && sudo ./result/bin/run-nixos-vm`
#nixosConfigurations.demo = nixpkgs.lib.nixosSystem {
# inherit system;
# specialArgs = { inherit self nixpkgs; };
# modules = [ hello-world-module ];
#};
};
}
The problem is that nix flake check will only pass when nixosConfigurations is not defined. When it is defined, it fails with this error:
… while calling 'fold''
at /nix/store/a27vy9akqhg36njid77z4bckjdbm3iyw-source/lib/lists.nix:56:15:
55| len = length list;
56| fold' = n:
| ^
57| if n == len
error:
Failed assertions:
- The ‘fileSystems’ option does not specify your root file system.
I suppose I could break this into two flakes, one for running the NixOS configuration and one for testing it, but that seems like I’ve missed something.
Any suggestions would be appreciated 