试金石

Explanation: A black hard stone, painted with a gold stripe, you can see the fineness of gold. Analogy accurate and reliable test methods. 　　Source: Yuan Ma Zhiyuan, "Jian Fu Bei" fourth off here, end, and now stood touchstone. " 　　Examples: Since ancient times, heroes, without the efforts toward the fu chaos, may not fulfill promises, so the foreign aggression of the enemy, the real hero of the piece of tempered ~ also. ★ Cai Dongfan "Qing Kingdoms" the second time