Getting stderr from a test::simple

neilwatson has asked for the wisdom of the Perl Monks concerning the following question:

Greetings,

Consider this code. When I run it, and there is an error, I never see the output from warn. Why is that, can I fix it, or am I doing it wrong?

#!/usr/bin/perl

use strict;
use warnings;
use Test::Simple tests => 1;

sub mycheck
{
   open( FH, '>', '/tmp/x/logfile' ) or return sub
      {
         warn "Cannot open file [$!]";
         return 1;
      };
   foreach my $line (<DATA>)
   {
      print FH $line or return sub
         {
            warn "Cannot write to file [$!]";
            return 2;
         };
   }
   close FH;
   return 0
}

ok( mycheck() == 0, "mycheck test" );

__DATA__
dr_test_class ;; empty ;; empty ;; empty ;; empty
dr_test_kept ;; handle_dr_test ;; /etc/dr_test ;; ;; kept ;; mojolicio
+us

$ ./foo.pl 
1..1
not ok 1 - mycheck test
#   Failed test 'mycheck test'
#   at ./foo.pl line 26.
# Looks like you failed 1 test of 1.
[download]

Neil Watson
watson-wilson.ca

Comment on Getting stderr from a test::simple Download Code

Replies are listed 'Best First'.
Re: Getting stderr from a test::simple by AppleFritter (Vicar) on Jul 01, 2014 at 18:05 UTC
Why do you expect this to print a warning? If the `open` call in `mycheck` fails, you return an anonymous subroutine. Test::Simple checks if this equals 0 (which it does not), so the test fails. At no point is the subroutine you return actually called, hence no warning.	[reply]
Re^2: Getting stderr from a test::simple by neilwatson (Priest) on Jul 01, 2014 at 18:10 UTC
I see. Would eval instead of sub be acceptable? Neil Watson watson-wilson.ca	[reply]
Re^3: Getting stderr from a test::simple by AppleFritter (Vicar) on Jul 01, 2014 at 18:26 UTC
Acceptable, probably, but if you merely want to print a warning in addition to making the test fail, I'd say `do` is your best choice: `open (FH, '>', '/tmp/x/logfile') or do { warn "Cannot open file [$!]"; return 1; };` [download] There may well be more idiomatic ways of doing (no pun intended) this that I'm not aware of. My monastic brothers will (probably) be happy to chime in!	[reply] [d/l]
Re: Getting stderr from a test::simple by Laurent_R (Canon) on Jul 01, 2014 at 18:01 UTC
Returning a reference to an anonymous subroutine does not mean that this subroutine will be executed.	[reply]
Re: Getting stderr from a test::simple by jeffa (Bishop) on Jul 02, 2014 at 14:42 UTC
Why are you returning sub refs? Try this instead: `use strict; use warnings; use Test::More tests => 1; sub mycheck { open( FH, '>', '/tmp/x/logfile' ) or return 1; foreach my $line (<DATA>) { print FH $line or return 2; } close FH; return 0 } my $return = mycheck(); is $return, 0, "got expected return value: $return"; __DATA__ dr_test_class ;; empty ;; empty ;; empty ;; empty dr_test_kept ;; handle_dr_test ;; /etc/dr_test ;; ;; kept ;; mojolicio +us` [download] Ahhhh, much better! :) jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l] [select]