#  set TEST flag before compiling tested module
use constant 'PKG::TEST' => 1; 

# ###  here normally use PKG
{
    package PKG;

    use strict;
    use warnings;
    use Data::Dump qw/pp dd/;
    use v5.16;





    sub create_output {
        my $count =shift;
    
        my $string;
        my $fh;

        my %hash;

        # create (mildly) complex demo HoA
        $hash{$_} = [reverse 1.. $count--]
            for "a".."f";

        # memorize datastructure when testing
        $PKG::TEST_result = \%hash if TEST;

        my $target = "c:/tmp/output.txt";

        #  redirect filehande to string when testing
        $target = \$PKG::TEST_content if TEST;
    
        open $fh, '>', $target;


        #  Output to "file"
        print $fh pp \%hash;
    }
}


# ### my tests
package main;

use B::Deparse;
use Data::Dump qw/pp dd/;


# prove that TEST code disappears unless TEST is true 
print B::Deparse->new->coderef2text(\&PKG::create_output);

PKG::create_output(5);

if ( PKG::TEST ) {
    use Test::More;

    my $expected ={
        a => [5, 4, 3, 2, 1],
        b => [4, 3, 2, 1],
        c => [3, 2, 1],
        d => [2, 1],
        e => [1],
        f => [],
    };
    
    is_deeply(
        $PKG::TEST_result,
        $expected,
        "internal result"
    );

    my $expected_str = pp $expected;
    
    is(
        $PKG::TEST_content,
        $expected_str,
        "file output"
    );

    done_testing();
}