UFC champion Jon Jones is adamantly denying any wrongdoing after a drug tester showed up at his place unannounced ... saying the whole interaction was as cordial as could be.
Jones -- a 36-year-old fighter -- claims he was at his home in Albuquerque, New Mexico last weekend ... when out of nowhere, a UFC-certified official showed up to test his blood while he was celebrating a birthday.
In a police report filed by the alleged tester, Jones is accused of grabbing the official's phone and threatening to kill her .