flake.nix

{
  name = "mbbx6spp-test";
  epoch = 2021;
  description = "A test of /proc fs inputs for a Hydra jobset";
  inputs = {
    uptime = builtins.readFile /proc/uptime;
    nixpkgs.url = "github:NixOS/nixpkgs/release-21.05";
  };
  outputs = { self, nixpkgs, uptime }: {
    checks."x86_64-linux".test = nixpkgs.hello.override { name = "hello-${uptime}"; };
  };
}