The plant pot test is a simple way for people in Snip's world to determine what element they are. They focus all their power in their hands and touch the plant pot. If the flower burns, their element is fire. If weeds grow in the pot, their element is nature. If the flower withers and dies, their power is darkness.
People who have the element Darkness often go on to do bad things, like killing people, or starting up criminal organisations.

Pins was scared that he'd become like them.