you are in your bollocks

Best definition
you are in your bollocks
A Dublin phrase used to express that you don’t think someone will do what they just claimed they would.
“Are” can often be replaced with “will” or “would” depending on the context.
If the “you” is changed to “I”, the “your” should be changed to “my”.
John: I’m the biggest legend in my class.

James: You are in your bollocks!

John: Paddy is an arsehole, I’ll kick the shit into him!

James: You will in your bollocks!

John: Paddy said he would beat you up if you keep slaggin’ him.

James: He would in his bollocks!

John: You’ll get the shit kicked into you by Paddy.

James: I will in my bollocks!