#!perl
use strict;
use warnings;
BEGIN {
    chdir 't' if -d 't';
    require './test.pl';
    set_up_inc('../lib');
        skip_all('Can\'t run under miniperl') if is_miniperl();
}
plan(19);
use IO::Handle; # ungetc()
my $s = 'foo';
Internals::SvREADONLY($s, 1);
eval{
        $s = 'bar';
};
like $@, qr/Modification of a read-only value/, '$s is readonly';
ok open(my $io, '<', \$s), 'open';
getc $io;
my $a = ord 'A';
note "buffer[$s]";
is $io->ungetc($a), $a, 'ungetc';
note "buffer[$s]";
is getc($io), chr($a), 'getc';
is $s, 'foo', '$s remains "foo"';
is getc($io), 'o', 'getc/2';
is getc($io), 'o', 'getc/3';
is getc($io), undef, 'getc/4';
for my $c($a .. ($a+10)){
        is $io->ungetc($c), $c, "ungetc($c)";
}