Ovid

There's a discussion on Perl-QA about whether the use of use_ok should be discouraged. I argue that it should be. It really doesn't gain us much, it's historically been buggy, and simply using the module is enough to cause a test failure if the module doesn't compile. So someone asked how to write this t/00-load.t if we didn't have use_ok:

#!perl -T
# -*- mode: cperl ; compile-command: "cd .. ; ./Build ; prove -vb t/00-*.t" -*-

use Test::More tests => 5;

BEGIN {
  use_ok( 'Test::Trap::Builder::TempFile' );
  use_ok( 'Test::Trap::Builder::SystemSafe' );
SKIP: {
    skip 'Lacking PerlIO', 1 unless eval "use PerlIO; 1";
    use_ok( 'Test::Trap::Builder::PerlIO' );
  }
  use_ok( 'Test::Trap::Builder' );
  use_ok( 'Test::Trap' ) or BAIL_OUT( "Nothing to test without the Test::Trap class" );    
}

diag( "Testing Test::Trap $Test::Trap::VERSION, Perl $], $^X" );

Here's a cleaner solution that relies on Perl's "use" builtin and the "if" pragma.

use Test::More tests => 1;

my $ok;
END { BAIL_OUT "Could not load all modules" unless $ok }
use Test::Trap::Builder::TempFile;                                                                                                            
use Test::Trap::Builder::SystemSafe;
use Test::Trap::Builder;
use Test::Trap;
use if eval "use PerlIO; 1", 'Test::Trap::Builder::PerlIO';
ok 1, 'All modules loaded successfully';
$ok = 1;

Yeah, I like that.

Naturally, it doesn't work if you're trying to dynamically discover the module names, but it could be made to work with that, too.

eval "use $module; 1"
  or BAIL_OUT $@ // "Zombie error";

Thanks to Ruud H.G. van Tol for correcting my eval.