test.pl

use v5.020;
use warnings;
use Mojo::UserAgent;

sub bsos_helper {
  my ( $server ) = @_;
  my $ua = Mojo::UserAgent->new;
  # XXX: Set proxy on $ua here
  $ua->on( start => sub {
    my ( $ua, $tx ) = @_;
    $tx->req->url->host( 'example.com' );
    $tx->req->url->port( '' );
  } );
  return $ua;
}

my $tx = bsos_helper( { server_id => 0 } )->get( '/foo' );
say "TX URL: " . $tx->req->url;

#######################################################################

sub build_tx {
  my ( $server, $path ) = @_;
  my $tx = Mojo::Transaction::HTTP->new;
  $tx->req->url->scheme( 'http' );
  $tx->req->url->host( 'example.com' );
  $tx->req->url->port( '' );
  # XXX: Set proxy on $tx->req here
  $tx->req->url->path( $path );
  return $tx;
}

$tx = build_tx( { server_id => 0 }, '/foo' );
$tx = Mojo::UserAgent->new->start( $tx );
say "TX URL: " . $tx->req->url;