Spin up Postgres for testing and connect to it during build/test

trusty · February 21, 2022, 12:39am

I’m interested in transitioning to Nix to build my Rust crate with cargo2nix. I managed to get the project building with Nix. But my integration tests (usually in Rust crates they are placed in a top-level tests directory) need a local Postgres instance. Is it possible to spin up an instance when I run nix build .#tests and tear it down right after?

I’m new to Nix ecosystem so it would be great if you can point me to a function I should be using.

erictapen · February 21, 2022, 10:48am

I’d be curious wether this works inside stdenv.mkDerivation, but from
what I know you’d need a NixOS integration test to achieve this task. In
the end it’s another Nix derivation, but you configure a whole NixOS
system in it, including a running Postgresql instance.

See

github.com

erictapen/nixpkgs/blob/95c4405a9b162303fa65b85a8491767e83366ac2/nixos/tests/mastodon/package-tests.nix

# Run the mastodon package tests.  They can't be run as part of the
# package build because they require PostgreSQL and Redis.
import ../make-test-python.nix ({ pkgs, ...} :
{
  name = "mastodon-package-tests";
  meta = with pkgs.lib.maintainers; {
    maintainers = [ happy-river ];
  };

  nodes = let
  in rec {
    machine =
      { ... }:
      {
        virtualisation.memorySize = 2048;
        virtualisation.diskSize = 1024;

        services.redis.enable = true;
        services.postgresql = {
          enable = true;

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for insipiration.