疾风劲草

lit. sturdy grass withstands high winds (idiom); fig. strength of character is revealed in a crisis

lit. sturdy grass withstands high winds and true gold stands the test of fire (idiom); fig. strength of character is revealed in a crisis

tough upright grass; (fig.) a staunch character who is loyal despite danger and hardship

true sentiments are seen in hard times (idiom); you see who your true friends are when you go through tough times together

to go through thick and thin (idiom)

to become more resolute with the passing of time (idiom)