nixpkgs/nixos/tests/swap-partition.nix

import ./make-test-python.nix ({ lib, pkgs, ... }:
{
  name = "swap-partition";

  nodes.machine =
    { config, pkgs, lib, ... }:
    {
      virtualisation.useDefaultFilesystems = false;

      virtualisation.rootDevice = "/dev/vda1";

      boot.initrd.postDeviceCommands = ''
        if ! test -b /dev/vda1; then
          ${pkgs.parted}/bin/parted --script /dev/vda -- mklabel msdos
          ${pkgs.parted}/bin/parted --script /dev/vda -- mkpart primary 1MiB -250MiB
          ${pkgs.parted}/bin/parted --script /dev/vda -- mkpart primary -250MiB 100%
          sync
        fi

        FSTYPE=$(blkid -o value -s TYPE /dev/vda1 || true)
        if test -z "$FSTYPE"; then
          ${pkgs.e2fsprogs}/bin/mke2fs -t ext4 -L root /dev/vda1
          ${pkgs.util-linux}/bin/mkswap --label swap /dev/vda2
        fi
      '';

      virtualisation.fileSystems = {
        "/" = {
          device = "/dev/disk/by-label/root";
          fsType = "ext4";
        };
      };

      swapDevices = [
        {
          device = "/dev/disk/by-label/swap";
        }
      ];
    };

  testScript = ''
    machine.wait_for_unit("multi-user.target")

    with subtest("Swap is active"):
      # Doesn't matter if the numbers reported by `free` are slightly off due to unit conversions.
      machine.succeed("free -h | grep -E 'Swap:\s+2[45][0-9]Mi'")
  '';
})