Best Practices for Network Tests during Nix-Build

Guides
1

Network test is not supported inside a nix-build except localhost.
How to use localhost and random port?
And is it better to use a network namespace?

2

This is an interesting question! I suspect the reason that no one tried an answer yet suggests that it is also a hard one. Could you elaborate what exactly you are trying to achieve, maybe with some sample code?

1 Like
3

If you’re trying to test network protocols and the like,try

4

What if you’re trying to leverage SQLx’s (Rust sql framework) compile-time verification?
Normally people spin up a PGDB in a docker container so as to allow this during compile-time (read: cargo build).

6

Wait I totally misunderstood thew whole stuff here.
SQLx does not use docker at all to create DBs during tests.
It uses the DATABASE_URL var you provide.
I was getting

message: "permission denied to create database"

But it was only because I did not set the right permissions for postgres user.

Working example here, in a nix flake, using crane + SQLx:

craneLib.buildPackage (commonArgs // {
          [...]
          preBuild = ''
            export DATABASE_URL=postgresql://postgres:postgres@localhost/test-db
            ${pkgs.postgresql}/bin/initdb -D .tmp/test-db
            ${pkgs.postgresql}/bin/pg_ctl -D .tmp/test-db -l .tmp/test-db.log -o "--unix_socket_directories='$PWD'" start
            ${pkgs.postgresql}/bin/createuser postgres -d -s -h $PWD
            ${pkgs.postgresql}/bin/createdb test-db -h $PWD --owner=postgres
            ${pkgs.sqlx-cli}/bin/sqlx migrate run
          '';
           [...]
}

Test works in rust with that, for me, no need for network access.
(Notice createuser postgres -d -s which adds the superuser -s and createdb -d roles)