Proof-of-Concept running PostgreSQL tests inside Nix package build

default.nix

with import <nixpkgs> { };
runCommand "some-test" {
    buildInputs = [ postgresql ];
    preCheck = ''
        set -e
        export PGDATA=$TMP/db
        export PGHOST=$TMP/socketdir
        mkdir $PGDATA $PGHOST
        pg_ctl initdb
        echo "unix_socket_directories = '$PGHOST'" >> $PGDATA/postgresql.conf
        pg_ctl start &
        trap "${procps}/bin/pkill postgres || true" EXIT
        sleep 1
        psql -d postgres -c "create database test"
    '';
    postCheck = ''
        psql -d postgres -c "drop database test"
        pg_ctl stop -m fast
    '';
} ''
  eval "$preCheck"

  whoops some error happend during check phase

  eval "$postCheck"
  touch $out
''