1)
How did Hashem test us?
1.
Rashi: Via affliction in exile. Radak - the remaining in Yisrael will say so after the refining - "v'Heveisi Es ha'Shelishis ba'Esh u'Tzeraftim ki'Tzerof Es ha'Kesef" (Zecharyah 13:9).
2)
What is the meaning of "Tzeraftanu"?
1.
Rashi: You make us repent to remove the dross from us, just like they refine silver to remove the dross from it. Malbim - they put silver in fire to refine it. Chazal say that they cast Menasheh in a copper pot and lit a fire under it.