-ok(!$@, "getdata from non-data wizard doesn't croak ($@)");
-ok(!defined($data), 'getdata from non-data wizard invalid returns undef');
+is($@, '', 'getdata from non-data wizard doesn\'t croak');
+is($data, undef, 'getdata from non-data wizard invalid returns undef');
+
+$wiz = wizard data => sub { ++$_[1] };
+my ($di, $ei) = (1, 10);
+my ($d, $e);
+cast $d, $wiz, $di;
+cast $e, $wiz, $ei;
+my $dd = getdata $d, $wiz;
+my $ed = getdata $e, $wiz;
+is($dd, 2, 'data from d is what we expected');
+is($di, 2, 'cast arguments from d were passed by alias');
+is($ed, 11, 'data from e is what we expected');
+is($ei, 11, 'cast arguments from e were passed by alias');
+$di *= 2;
+$dd = getdata $d, $wiz;
+$ed = getdata $e, $wiz;
+is($dd, 2, 'data from d wasn\'t changed');
+is($ed, 11, 'data from e wasn\'t changed');