The Patience Tester is a treasure in Pikmin 2, it is actually a a can of Sun Luck water chestnuts. It is found on Sublevel 3 of the Citadel of Spiders, and is usually hidden in an alcove, sometimes blocked by a wall. There are a few Anode Beetles that might hinder the Pikmin when recovering the treasure.
Notes
Olimar's Journal
"Patience Tester/journal"
Sales Pitch
"Patience Tester/sale"