nixpkgs/nixos/tests/earlyoom.nix

import ./make-test-python.nix (
  { lib, ... }:
  {
    name = "earlyoom";
    meta = {
      maintainers = with lib.maintainers; [
        ncfavier
        oxalica
      ];
    };

    nodes.machine =
      { pkgs, ... }:
      {
        # Limit VM resource usage.
        virtualisation.memorySize = 1024;

        services.earlyoom = {
          enable = true;
          # Use SIGKILL, or `tail` will catch SIGTERM and exit successfully.
          freeMemKillThreshold = 90;
        };

        systemd.services.testbloat = {
          description = "Create a lot of memory pressure";
          serviceConfig = {
            ExecStart = "${pkgs.coreutils}/bin/tail /dev/zero";
          };
        };
      };

    testScript = ''
      machine.wait_for_unit("earlyoom.service")

      with subtest("earlyoom should kill the bad service"):
          machine.fail("systemctl start --wait testbloat.service")
          assert machine.get_unit_info("testbloat.service")["Result"] == "signal"
          output = machine.succeed('journalctl -u earlyoom.service -b0')
          assert 'low memory! at or below SIGKILL limits' in output
    '';
  }
)