Updated nixpkgs to the latest and it worked:
let
pkgs = import (builtins.fetchTarball {
name = "nixos-unstable-2024-07-27";
url = "https://github.com/nixos/nixpkgs/archive/ff934de1da331e61653685718ebf802e844a1833.tar.gz";
sha256 = "sha256:100pr2xq06kzhbyzxfsyhmx1kxfnjvsl5fwv4idcv7x31xx3p06k";
}) { };
nodeName = "debug";
in
pkgs.testers.runNixOSTest {
name = "debug";
nodes.${nodeName} = { };
testScript = ''
breakpoint()
'';
}
Perhaps the version from 2024-06-05
had some issues.