" I want to test him, said Saphira. She slapped her tail against the ground, causing Fírnen to pause.
Test him? How? For what?
To find out if he has the iron in his bones and the fire in his belly to match me.
Are you sure? he asked, understanding her intent.
She again slapped her tail against the ground, and he felt her certainty and the strength of her desire. I know everything about him--everything but this. Besides--she displayed a flash of amusement--it’s not as if dragons mate for life.
Very well…But be careful.
He had barely finished speaking when Saphira lunged forward and bit Fírnen on his left flank, drawing blood and causing Fírnen to snarl and spring backward. The green dragon growled, appearing uncertain of himself, and retreated before Saphira as she prowled toward him.
Saphira! Chagrined, Eragon turned to Arya, intending to apologize.
Arya did not seem upset. To Fírnen, and to Eragon as well, she said, If you want her to respect you, then you have to bite her in return.
She raised an eyebrow at Eragon, and he responded with a wry smile, understanding.
Fírnen glanced at Arya and hesitated. He jumped back as Saphira snapped at him again. Then he roared and lifted his wings, as if to make himself appear larger, and he charged Saphira--and nipped her on a hind leg, sinking his teeth into her hide.
The pain Saphira felt was not pain.
Saphira and Fírnen resumed circling, growling and yowling with increasing volume. Then Fírnen jumped at her again. He landed on Saphira’s neck and bore her head to the ground, where he held her pinned and gave her a pair of playful bites at the base of her skull.
Saphira did not struggle as fiercely as Eragon would have expected, and he guessed that she had allowed Fírnen to catch her, as it was not something even Thorn had managed to do.
“The courting of dragons is no gentle affair,” he said to Arya.
“Did you expect soft words and tender caresses?”
“I suppose not.”
With a heave of her neck, Saphira threw Fírnen off and scrambled backward. She roared and clawed at the ground with her forefeet, and then Fírnen lifted his head toward the sky and loosed a rippling pennant of green fire twice the length of his own body.
“Oh!” exclaimed Arya, sounding delighted.
“What?”
“That’s the first time he has breathed fire! "

― Christopher Paolini , Inheritance (The Inheritance Cycle, #4)