Pokémon: The Series Rewrite:Indigo League Part 1

Episode 53: The Ultimate Test

Ash and group arrive at a Pokémon testing facility where u take a test to become a gym leader which Misty and Brock reminisce about them taking the test. Ash decides to take the test leading to Team Rocket doing it to try to take over the Viridian City Gym as it's revealed to have been abandoned. But Ash is the one to pass the test and gets a card which means he could be able to work his own Pokémon gym.