Endure the trial.
Trial in a “refining pot” (lesser difficulty) = produces silver.
Trial in a “furnace” (higher difficulty) = produces gold.
What is “tested/tried”? The “heart”.
By Whom? God.
Proof verse (taken literally):
“A refining pot [is] for silver, and a furnace for gold, And the trier of hearts [is] Jehovah.” (Proverbs 17:3)