it is to improve my work

me as a content creator for the marketplace and as a server moderator the commands are important but what I want to report  It is about the commands, and it is that the one of the items does not work well. I want to detect a certain item and the command does not work is the following. /testfor @a [hasitem\{item=shulker_box,data=6}]  ,the data of the object does not grab which it would be good to fix it