my $stdout = '';
        eval {
        *STDOUT = new IO::Tee(
        \*STDERR, IO::Scalar->new(\$stdout));
        $ok = runtests(@tests);
        };
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write() on unopened filehandle STDOUT at /usr/lib/perl5/vendor_perl/5.
+8.2/Test/Harness.pm line 665.
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Thanks!

water

I don't have IO::Scalar, but the following works. Downside: requires perl 5.8.0 or higher.

use 5.8.0;  # for open \$buf.
use strict;
use warnings;

use IO::Tee ();

my $stdout = '';

{
   my $fh_scalar;
   open($fh_scalar, '>', \$stdout)
   or die("Can't open \$stdout: $!\n");


   local *STDOUT = new IO::Tee(
      \*STDERR,
      $fh_scalar
   );


   print("Test\n");
}

print("\n");

print("\$stdout:\n");
print($stdout);
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I added local to easily restore the original STDOUT, but it's not needed.

Thanks, but I tried your code and still get

write() on unopened filehandle STDOUT at /usr/lib/perl5/vendor_perl/5.
+8.2/Test/Harness.pm line 665.
[download]

Maybe this has something to do with the magic internals and filehandle remapping already going on in Test::Harness?

Testing stuff written to stdout has been discussed a few times on the perl-qa mailing list. As far as possible, I use Ovid's trick of something like:

sub Foo::_print { print shift }
[download]

Then in my test, something like this:

my $_print;
*Foo::_print = sub { $_print = shift };
is($_print, $expected, "Foo::_print output the correct data");
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Apart from sparing you worrying about Test::Harness choking, it makes the module a little more flexible in that you can (a little hackily) override the _print function if you need to alter the module behaviour.

If you can't use a _print() function for some reason, there are many other approaches as discussed here and here and here and here. For an example of using tie, see the file TieOut.pm in the ExtUtils-MakeMaker CPAN distribution.