+ok( $o->del( $_ ), "del $_" ) foreach map { "key-$_" } ( 'next', 'left' );
+ok( ! $o->del('non-existing' ), 'del non-existing' );
+
+cmp_ok( $o->type('foo'), 'eq', 'string', 'type' );
+
+cmp_ok( $o->keys('key-*'), '==', $key_next + 1, 'key-*' );
+is_deeply( [ $o->keys('key-*') ], [ @keys ], 'keys' );
+
+ok( my $key = $o->randomkey, 'randomkey' );
+diag "key: $key";