use strict;
use warnings;

use Test::More;


use Encode qw( is_utf8 encode_utf8 );


use Inline C => <<'__EOC__';

void candidate(SV* sv) {
   dXSARGS;
   STRLEN len;
   char* buf = SvPV(sv, len);
   SP[0] = sv_2mortal(newSVpvn(buf, len));
   XSRETURN(1);
}

__EOC__

sub baseline { is_utf8($_[0]) ? encode_utf8($_[0]) : $_[0] }

sub _u { my ($s) = @_; utf8::upgrade($s);   $s }
sub _d { my ($s) = @_; utf8::downgrade($s); $s }

sub printable { sprintf("%v04X", $_[0]) }


my @tests = (
   [ '00-7F',        "a"           ],
   [ '80-FF,UTF8=0', _d(chr(0xE9)) ],
   [ '80-FF,UTF8=1', _u(chr(0xE9)) ],
   [ '>FF',          chr(0x2660)   ],
);

plan tests => 0+@tests;

for (@tests) {
   my ($test_name, $input) = @$_;
   my $got = candidate($input);
   my $expected = baseline($input);
   #is($got, $expected, $test_name);
   is(printable($got), printable($expected), $test_name);
}

##</code><code>##

1..4
ok 1 - 00-7F
ok 2 - 80-FF,UTF8=0
ok 3 - 80-FF,UTF8=1
ok 4 - >FF

##</code><code>##

my @tests = (
   [ '00-7F',        "a"           ],
   [ '80-FF,UTF8=0', _d(chr(0xE9)) ],
   [ '80-FF,UTF8=1', _u(chr(0xE9)) ],
   [ '>FF',          chr(0x2660)   ],
);

plan tests => 0+@tests;

my $dbh = ... connect and setup as you wish ...

my $sth = $dbh->prepare('SELECT ?');
for (@tests) {
   my ($test_name, $input) = @$_;

   $sth->execute($input) or die;
   my $row = $sth->fetch() or die;
   $sth->finish() or die if $row;

   my $got = $row->[0];  
   is(printable($got), printable($input), $test_name);
}