test your mettle

Originally, mettle was simply a variant spelling of the word metal (which dates to at least the 13th century), and it was used in all of the same senses as its metallic relative. Over time, however, mettle came to be used mainly in figurative senses referring to the quality of someone’s character. It eventually became a distinct English word in its own right, losing its literal sense altogether. Metal remained a term primarily used for those hard, shiny substances such as steel or iron, but it also acquired a figurative use. Today, both words can mean “vigor and strength of spirit or temperament,” but only metal is used of metallic substances.
courage, mettle, spirit, resolution, tenacity mean mental or moral strength to resist opposition, danger, or hardship. courage implies firmness of mind and will in the face of danger or extreme difficulty. the courage to support unpopular causes mettle suggests an ingrained capacity for meeting strain or difficulty with fortitude and resilience. a challenge that will test your mettle spirit also suggests a quality of temperament enabling one to hold one’s own or keep up one’s morale when opposed or threatened. her spirit was unbroken by failure resolution stresses firm determination to achieve one’s ends. the resolution of pioneer women tenacity adds to resolution implications of stubborn persistence and unwillingness to admit defeat. held to their beliefs with great tenacity

Green’s nurse was part of a whole high-class wife-swapping thing he’d somehow got himself involved in, but for which he and his acting were unprepared. His range stretches form cheeky to confused to – as long as he gets a breather every so often-sometimes cheeky but confused.
Actually, it would be unfair to concentrate on the bloodier bits of Nurses, which is not a series that exploits the gory side of the A&E just to keep things tense. There are plenty of these medical fly-on-the-walls all over the schedules, and they are by and large more exploitative as they parachute Gabby Roslin or Carol; Vordeman in to wring every last drop of pathos out of the children’s ward.

Demonstrate your true character.
By the turn of the 18th century though the two spellings had begun to diverge. ‘Mettle’ was usually reserved for ‘character, disposition – the stuff we are made of’, for example:

test your mettle, Language Skills Abroad
Shakespeare could never have imagined the extent to which his work would endure. That’s where we have the advantage. (And how often can you say that?) We deliberately build our bikes to last because we believe in sustainability. The same applies to our clothing. The Insulated Jacket is, crucially, made almost entirely from recycled materials. For instance, 70% of the fabric used in the chest and arms is produced from recycled polyester. And the back of the jacket fares even better, being made from a fully recycled Italian ‘Roubaix’ material. That’s 78% recycled nylon and 22% recycled Lycra, to be precise. What you might call boring but important.
At Pearson, we design the bikes in our Road collection to ensure you get the most from your riding experience. We design them to provide an optimal position, then build them to guarantee years of comfortable use. It’s a philosophy we’ve carried over into our new collection of Road clothing.

test your mettle, Language Skills Abroad
To test your mettle is to demonstrate resolve and determination; to be tenacious.
Usually associated with strength or courage, to test your mettle is to demonstrate resolve and determination; to be tenacious. Hardly surprising then that today, it’s a phrase mostly heard in sporting circles, or read in news headlines to describe athletic grit.

Resources:

http://www.irishtimes.com/news/many-ways-to-test-your-mettle-1.322209?mode=amp
http://www.english-for-students.com/Test-Your-Mettle.html
http://medium.com/@Pearson1860/test-your-mettle-b45830a01348
http://www.yourlifechoices.com.au/fun/entertainment/test-your-mettle
http://www-personal.umich.edu/~cellis/heteronym.html