The 21-year old midfielder and his Scotland teammates are preparing for Sunday's friendly with Brazil at the Emirates Stadium in London and McAllister, who represented the Scots close to 60 times, says it's a great opportunity for the Leeds United loanee.
"It is a great opportunity to test yourself against the world's best as far I'm concerned," McAllister told the club's official website.
"I know Spain are the World Cup holders but I always feel that Brazil bring something very special so it'll be a decent crowd.
"I think the Jocks will take over Trafalgar Square again probably and I might go down myself to watch the game.
"It is a high-profile game against some of the best players in the world so it will be a good game for Barry and for Scotland.
"I think Craig Levein has got things moving positively and has a few very talented midfield players but it'll be a good test for Barry and a good game.
"Sometimes at this stage of the season you get these so-called meaningless friendlies but this game has got a bit of spice because of who the opponents are so everybody will enjoy it."