The Pokémon test refers to an argument made by Wikipedians, beginning in the mid-2000s, to determine whether some articles should be deleted or not. The argument generally went like this: If some barely known Pokémon character has its own page, then surely so can any old bus stop.
The argument could go either way: as a reason to keep, or delete. And the measuring stick was Pokémon.
In Wikipedia's early days, it was chock full of stub articles on individual fictional Pokémon characters, many of them not notable enough for their own entries. Editors reached consensus and the articles were ultimately merged into List of Pokémon.
The argument is flawed, as the essay notes, but important and interesting nonetheless. And one that continues to this day; they might not cite Pokémon, but editors still point to other less-than-notable topics in an attempt to boost the notability of their own.