use strict;
use warnings;

use Test::More 'tests' => 7;

sub empty_string { '' }
sub no_replacement { my $x = 'x'; return ($x =~ s/y//); }

my $warning;
$SIG{__WARN__} = sub { $warning = shift };

ok( ! defined $warning, 'no warning recorded' );
is( 0+empty_string(), 0, 'empty string is zero' );
ok( $warning, 'warning is generated' );
my $expected_warning = q{Argument "" isn't numeric in addition (+)};
is( substr( $warning, 0, length $expected_warning ),
    $expected_warning,
    q{warning is the one that's expected} );

undef $warning;
ok( ! defined $warning, 'recorded warning is cleared' );
is( 0+no_replacement(), 0, 'no replacement is zero' );
ok( ! defined $warning, 'no warning is generated' );