cmp_ok( $o->get( "key-$_" ), 'eq', $_, "get key-$_" );
cmp_ok( $o->incr( 'key-next' ), '==', $_ + 1, 'incr' );
cmp_ok( $o->decr( 'key-left' ), '==', $key_next - $_ - 1, 'decr' );
cmp_ok( $o->get( "key-$_" ), 'eq', $_, "get key-$_" );
cmp_ok( $o->incr( 'key-next' ), '==', $_ + 1, 'incr' );
cmp_ok( $o->decr( 'key-left' ), '==', $key_next - $_ - 1, 'decr' );