How to check if a player has an achievement?

Hey guys, so I'm new to this whole modding scene (I just got MCreator yesterday, and so far it looks fun!) and I need some help. I was messing around and was trying to create a block that gives me an advancement and sends me a message, but only when I don't have a specific advancement, but I'm having a problem where it keeps sending the message despite the fact that I have the advancement. Like I said, I'm new, so I'm probably just being dumb right now. If it helps, I'm using the 1.12.2 version of MCreator.

(I'm having trouble uploading an image, sorry. If it helps, I'm using an if statement with a logic variable that goes something along the lines of "if: get Local:has_test_achievement=false do: the rest of the code)