use warnings;
use strict;
use Test::More tests=>2;
use Test::NoWarnings;
use Test::Warn;

sub Foo::get_member_id_by_name { warn "foo than bar" };
my $obj = bless {}, 'Foo';

warning_like ( sub { $obj->get_member_id_by_name('smith'); },
	qr/than/, 'warns when more than one name returned' );

__END__

1..2
ok 1 - warns when more than one name returned
ok 2 - no warnings

##</code><code>##

sub warns (&) {
	my $sub = shift;
	my @warns;
	{ local $SIG{__WARN__} = sub { push @warns, shift }; $sub->() }
	return wantarray ? @warns : scalar @warns;
}

print "<$_>\n" for warns { warn "Hello"; warn "World" }

__END__
<Hello at - line 8.
>
<World at - line 8.
>