you can edit the post and put the link next to the pattern claimed! what i normally put is
COMPLETED BY [username] on [date] (IN TESTING! [tester call link])
but you can do it however you want to! 
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edited to add since i found the tester call haha:
this is how i’d personally put it next to the pattern in the list! but again, put the link/format in however you want to.
COMPLETED BY Francrochet on May 7, 2025 (IN TESTING! Tester call for Crochet: Ivy purse)
and then maybe DM the person who requested the pattern or tag them here in the comments that the tester call is out? i’m not sure which is preferred so maybe axo or someone else can weigh in on that part. hopefully this was helpful and wasn’t too confusing of an explanation! 