The Ospreys, who had the weekend off, are on a fine run of form however and have won their last six RaboDirect PRO12 matches, including a 23-22 victory over Leinster at the RDS - where the final will be played.
The Welsh region also recorded a stunning 45-10 win over defending champions Munster in their semi-final and Tandy revealed he has virtually a full strength squad to pick from.
"[There will be] one late test on one position. He is part of the 23 and we'll make that decision and it will be announced on Friday," said Tandy.
"We are going to need an exceptional performance to hopefully stand on the podium on Sunday.
"They [Leinster] are a fantastic team there is no getting away from it. To win the Heineken Cup three times in four years takes some doing.
"But hopefully we can go there on Sunday and spoil the party.
"We have done really well to beat them twice this season but that will count for nothing come Sunday.
"There is a realisation that to go and win in Leinster you have got to be at the top of your game to be in a contest."
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